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    Command:

    nmap

    
    
    

    SYNOPSIS

           nmap [Scan Type...] [Options] {target specification}
    
    
    

    DESCRIPTION

           Nmap ("Network Mapper") is an open source tool for network exploration
           and security auditing. It was designed to rapidly scan large networks,
           although it works fine against single hosts. Nmap uses raw IP packets
           in novel ways to determine what hosts are available on the network,
           what services (application name and version) those hosts are offering,
           what operating systems (and OS versions) they are running, what type of
           packet filters/firewalls are in use, and dozens of other
           characteristics. While Nmap is commonly used for security audits, many
           systems and network administrators find it useful for routine tasks
           such as network inventory, managing service upgrade schedules, and
           monitoring host or service uptime.
    
           The output from Nmap is a list of scanned targets, with supplemental
           information on each depending on the options used. Key among that
           information is the "interesting ports table"..  That table lists the
           port number and protocol, service name, and state. The state is either
           open, filtered, closed, or unfiltered.  Open.  means that an
           application on the target machine is listening for connections/packets
           on that port.  Filtered.  means that a firewall, filter, or other
           network obstacle is blocking the port so that Nmap cannot tell whether
           it is open or closed.  Closed.  ports have no application listening on
           them, though they could open up at any time. Ports are classified as
           unfiltered.  when they are responsive to Nmap?s probes, but Nmap cannot
           determine whether they are open or closed. Nmap reports the state
           combinations open|filtered.  and closed|filtered.  when it cannot
           determine which of the two states describe a port. The port table may
           also include software version details when version detection has been
           requested. When an IP protocol scan is requested (-sO), Nmap provides
           information on supported IP protocols rather than listening ports.
    
           In addition to the interesting ports table, Nmap can provide further
           information on targets, including reverse DNS names, operating system
           guesses, device types, and MAC addresses.
    
           A typical Nmap scan is shown in Example 1. The only Nmap arguments used
           in this example are -A, to enable OS and version detection, script
           scanning, and traceroute; -T4 for faster execution; and then the two
           target hostnames.
    
           Example 1. A representative Nmap scan
    
               # nmap -A -T4 scanme.nmap.org
    
               Starting Nmap ( http://nmap.org )
               Interesting ports on scanme.nmap.org (64.13.134.52):
               Not shown: 994 filtered ports
               PORT    STATE  SERVICE VERSION
               22/tcp  open   ssh     OpenSSH 4.3 (protocol 2.0)
               9   11.00 metro0.sv.svcolo.com (208.185.168.173)
               10  9.93  scanme.nmap.org (64.13.134.52)
    
               Nmap done: 1 IP address (1 host up) scanned in 17.00 seconds
    
           The newest version of Nmap can be obtained from http://nmap.org. The
           newest version of this man page is available at
           http://nmap.org/book/man.html.  It is also included as a chapter of
           Nmap Network Scanning: The Official Nmap Project Guide to Network
           Discovery and Security Scanning (see http://nmap.org/book/).
    
    
    

    OPTIONS SUMMARY

           This options summary is printed when Nmap is run with no arguments, and
           the latest version is always available at
           http://nmap.org/data/nmap.usage.txt. It helps people remember the most
           common options, but is no substitute for the in-depth documentation in
           the rest of this manual. Some obscure options aren?t even included
           here.
    
               Nmap 5.21 ( http://nmap.org )
               Usage: nmap [Scan Type(s)] [Options] {target specification}
               TARGET SPECIFICATION:
                 Can pass hostnames, IP addresses, networks, etc.
                 Ex: scanme.nmap.org, microsoft.com/24, 192.168.0.1; 10.0.0-255.1-254
                 -iL <inputfilename>: Input from list of hosts/networks
                 -iR <num hosts>: Choose random targets
                 --exclude <host1[,host2][,host3],...>: Exclude hosts/networks
                 --excludefile <exclude_file>: Exclude list from file
               HOST DISCOVERY:
                 -sL: List Scan - simply list targets to scan
                 -sP: Ping Scan - go no further than determining if host is online
                 -PN: Treat all hosts as online -- skip host discovery
                 -PS/PA/PU/PY[portlist]: TCP SYN/ACK, UDP or SCTP discovery to given ports
                 -PE/PP/PM: ICMP echo, timestamp, and netmask request discovery probes
                 -PO[protocol list]: IP Protocol Ping
                 -n/-R: Never do DNS resolution/Always resolve [default: sometimes]
                 --dns-servers <serv1[,serv2],...>: Specify custom DNS servers
                 --system-dns: Use OS?s DNS resolver
                 --traceroute: Trace hop path to each host
               SCAN TECHNIQUES:
                 -sS/sT/sA/sW/sM: TCP SYN/Connect()/ACK/Window/Maimon scans
                 -sU: UDP Scan
                 -sN/sF/sX: TCP Null, FIN, and Xmas scans
                 --scanflags <flags>: Customize TCP scan flags
                 -sI <zombie host[:probeport]>: Idle scan
                 -sY/sZ: SCTP INIT/COOKIE-ECHO scans
                 -sO: IP protocol scan
                 -b <FTP relay host>: FTP bounce scan
               PORT SPECIFICATION AND SCAN ORDER:
                 -p <port ranges>: Only scan specified ports
                   Ex: -p22; -p1-65535; -p U:53,111,137,T:21-25,80,139,8080
                 -F: Fast mode - Scan fewer ports than the default scan
                 --script-trace: Show all data sent and received
                 --script-updatedb: Update the script database.
               OS DETECTION:
                 -O: Enable OS detection
                 --osscan-limit: Limit OS detection to promising targets
                 --osscan-guess: Guess OS more aggressively
               TIMING AND PERFORMANCE:
                 Options which take <time> are in milliseconds, unless you append ?s?
                 (seconds), ?m? (minutes), or ?h? (hours) to the value (e.g. 30m).
                 -T<0-5>: Set timing template (higher is faster)
                 --min-hostgroup/max-hostgroup <size>: Parallel host scan group sizes
                 --min-parallelism/max-parallelism <time>: Probe parallelization
                 --min-rtt-timeout/max-rtt-timeout/initial-rtt-timeout <time>: Specifies
                     probe round trip time.
                 --max-retries <tries>: Caps number of port scan probe retransmissions.
                 --host-timeout <time>: Give up on target after this long
                 --scan-delay/--max-scan-delay <time>: Adjust delay between probes
                 --min-rate <number>: Send packets no slower than <number> per second
                 --max-rate <number>: Send packets no faster than <number> per second
               FIREWALL/IDS EVASION AND SPOOFING:
                 -f; --mtu <val>: fragment packets (optionally w/given MTU)
                 -D <decoy1,decoy2[,ME],...>: Cloak a scan with decoys
                 -S <IP_Address>: Spoof source address
                 -e <iface>: Use specified interface
                 -g/--source-port <portnum>: Use given port number
                 --data-length <num>: Append random data to sent packets
                 --ip-options <options>: Send packets with specified ip options
                 --ttl <val>: Set IP time-to-live field
                 --spoof-mac <mac address/prefix/vendor name>: Spoof your MAC address
                 --badsum: Send packets with a bogus TCP/UDP/SCTP checksum
                 --adler32: Use deprecated Adler32 instead of CRC32C for SCTP checksums
               OUTPUT:
                 -oN/-oX/-oS/-oG <file>: Output scan in normal, XML, s|<rIpt kIddi3,
                    and Grepable format, respectively, to the given filename.
                 -oA <basename>: Output in the three major formats at once
                 -v: Increase verbosity level (use twice or more for greater effect)
                 -d[level]: Set or increase debugging level (Up to 9 is meaningful)
                 --reason: Display the reason a port is in a particular state
                 --open: Only show open (or possibly open) ports
                 --packet-trace: Show all packets sent and received
                 --iflist: Print host interfaces and routes (for debugging)
                 --log-errors: Log errors/warnings to the normal-format output file
                 --append-output: Append to rather than clobber specified output files
                 --resume <filename>: Resume an aborted scan
                 --stylesheet <path/URL>: XSL stylesheet to transform XML output to HTML
                 --webxml: Reference stylesheet from Nmap.Org for more portable XML
                 --no-stylesheet: Prevent associating of XSL stylesheet w/XML output
               MISC:
                 -6: Enable IPv6 scanning
                 -A: Enables OS detection and Version detection, Script scanning and Traceroute
                 --datadir <dirname>: Specify custom Nmap data file location
                 --send-eth/--send-ip: Send using raw ethernet frames or IP packets
    
           Sometimes you wish to scan a whole network of adjacent hosts. For this,
           Nmap supports CIDR-style.  addressing. You can append /numbits to an
           IPv4 address or hostname and Nmap will scan every IP address for which
           the first numbits are the same as for the reference IP or hostname
           given. For example, 192.168.10.0/24 would scan the 256 hosts between
           192.168.10.0 (binary: 11000000 10101000 00001010 00000000) and
           192.168.10.255 (binary: 11000000 10101000 00001010 11111111),
           inclusive. 192.168.10.40/24 would scan exactly the same targets. Given
           that the host scanme.nmap.org.  is at the IP address 64.13.134.52, the
           specification scanme.nmap.org/16 would scan the 65,536 IP addresses
           between 64.13.0.0 and 64.13.255.255. The smallest allowed value is /0,
           which scans the whole Internet. The largest value is /32, which scans
           just the named host or IP address because all address bits are fixed.
    
           CIDR notation is short but not always flexible enough. For example, you
           might want to scan 192.168.0.0/16 but skip any IPs ending with .0 or
           .255 because they may be used as subnet network and broadcast
           addresses. Nmap supports this through octet range addressing. Rather
           than specify a normal IP address, you can specify a comma-separated
           list of numbers or ranges for each octet. For example,
           192.168.0-255.1-254 will skip all addresses in the range that end in .0
           or .255, and 192.168.3-5,7.1 will scan the four addresses 192.168.3.1,
           192.168.4.1, 192.168.5.1, and 192.168.7.1. Either side of a range may
           be omitted; the default values are 0 on the left and 255 on the right.
           Using - by itself is the same as 0-255, but remember to use 0- in the
           first octet so the target specification doesn?t look like a
           command-line option. Ranges need not be limited to the final octets:
           the specifier 0-255.0-255.13.37 will perform an Internet-wide scan for
           all IP addresses ending in 13.37. This sort of broad sampling can be
           useful for Internet surveys and research.
    
           IPv6 addresses can only be specified by their fully qualified IPv6
           address or hostname. CIDR and octet ranges aren?t supported for IPv6
           because they are rarely useful.
    
           Nmap accepts multiple host specifications on the command line, and they
           don?t need to be the same type. The command nmap scanme.nmap.org
           192.168.0.0/8 10.0.0,1,3-7.- does what you would expect.
    
           While targets are usually specified on the command lines, the following
           options are also available to control target selection:
    
           -iL inputfilename (Input from list) .
               Reads target specifications from inputfilename. Passing a huge list
               of hosts is often awkward on the command line, yet it is a common
               desire. For example, your DHCP server might export a list of 10,000
               current leases that you wish to scan. Or maybe you want to scan all
               IP addresses except for those to locate hosts using unauthorized
               static IP addresses. Simply generate the list of hosts to scan and
               pass that filename to Nmap as an argument to the -iL option.
               Entries can be in any of the formats accepted by Nmap on the
               Keep in mind that some network administrators bristle at
               unauthorized scans of their networks and may complain. Use this
               option at your own risk! If you find yourself really bored one
               rainy afternoon, try the command nmap -sS -PS80 -iR 0 -p 80 to
               locate random web servers for browsing.
    
           --exclude host1[,host2[,...]] (Exclude hosts/networks) .
               Specifies a comma-separated list of targets to be excluded from the
               scan even if they are part of the overall network range you
               specify. The list you pass in uses normal Nmap syntax, so it can
               include hostnames, CIDR netblocks, octet ranges, etc. This can be
               useful when the network you wish to scan includes untouchable
               mission-critical servers, systems that are known to react adversely
               to port scans, or subnets administered by other people.
    
           --excludefile exclude_file (Exclude list from file) .
               This offers the same functionality as the --exclude option, except
               that the excluded targets are provided in a newline, space, or tab
               delimited exclude_file rather than on the command line.
    
               The exclude file may contain comments that start with # and extend
               to the end of the line.
    
    
    

    HOST DISCOVERY

           One of the very first steps in any network reconnaissance mission is to
           reduce a (sometimes huge) set of IP ranges into a list of active or
           interesting hosts. Scanning every port of every single IP address is
           slow and usually unnecessary. Of course what makes a host interesting
           depends greatly on the scan purposes. Network administrators may only
           be interested in hosts running a certain service, while security
           auditors may care about every single device with an IP address. An
           administrator may be comfortable using just an ICMP ping to locate
           hosts on his internal network, while an external penetration tester may
           use a diverse set of dozens of probes in an attempt to evade firewall
           restrictions.
    
           Because host discovery needs are so diverse, Nmap offers a wide variety
           of options for customizing the techniques used. Host discovery is
           sometimes called ping scan, but it goes well beyond the simple ICMP
           echo request packets associated with the ubiquitous ping tool. Users
           can skip the ping step entirely with a list scan (-sL) or by disabling
           ping (-PN), or engage the network with arbitrary combinations of
           multi-port TCP SYN/ACK, UDP, SCTP INIT and ICMP probes. The goal of
           these probes is to solicit responses which demonstrate that an IP
           address is actually active (is being used by a host or network device).
           On many networks, only a small percentage of IP addresses are active at
           any given time. This is particularly common with private address space
           such as 10.0.0.0/8. That network has 16 million IPs, but I have seen it
           used by companies with less than a thousand machines. Host discovery
           can find those machines in a sparsely allocated sea of IP addresses.
    
           If no host discovery options are given, Nmap sends an ICMP echo
           local ethernet network even if you specify other -P* options, because
           it is almost always faster and more effective.
    
           By default, Nmap does host discovery and then performs a port scan
           against each host it determines is online. This is true even if you
           specify non-default host discovery types such as UDP probes (-PU). Read
           about the -sP option to learn how to perform only host discovery, or
           use -PN to skip host discovery and port scan all target hosts. The
           following options control host discovery:
    
           -sL (List Scan) .
               The list scan is a degenerate form of host discovery that simply
               lists each host of the network(s) specified, without sending any
               packets to the target hosts. By default, Nmap still does
               reverse-DNS resolution on the hosts to learn their names. It is
               often surprising how much useful information simple hostnames give
               out. For example, fw.chi is the name of one company?s Chicago
               firewall.  Nmap also reports the total number of IP addresses at
               the end. The list scan is a good sanity check to ensure that you
               have proper IP addresses for your targets. If the hosts sport
               domain names you do not recognize, it is worth investigating
               further to prevent scanning the wrong company?s network.
    
               Since the idea is to simply print a list of target hosts, options
               for higher level functionality such as port scanning, OS detection,
               or ping scanning cannot be combined with this. If you wish to
               disable ping scanning while still performing such higher level
               functionality, read up on the -PN (skip ping) option.
    
           -sP (Skip port scan) .
               This option tells Nmap not to do a port scan after host discovery,
               and only print out the available hosts that responded to the scan.
               This is often known as a "ping scan", but you can also request that
               traceroute and NSE host scripts be run. This is by default one step
               more intrusive than the list scan, and can often be used for the
               same purposes. It allows light reconnaissance of a target network
               without attracting much attention. Knowing how many hosts are up is
               more valuable to attackers than the list provided by list scan of
               every single IP and host name.
    
               Systems administrators often find this option valuable as well. It
               can easily be used to count available machines on a network or
               monitor server availability. This is often called a ping sweep, and
               is more reliable than pinging the broadcast address because many
               hosts do not reply to broadcast queries.
    
               The -sP option sends an ICMP echo request, TCP SYN to port 443, TCP
               ACK to port 80, and an ICMP timestamp request by default. When
               executed by an unprivileged user, only SYN packets are sent (using
               a connect call) to ports 80 and 443 on the target. When a
               privileged user tries to scan targets on a local ethernet network,
               ARP requests are used unless --send-ip was specified. The -sP
               attempt the requested scanning functions against every target IP
               address specified. So if a class B sized target address space (/16)
               is specified on the command line, all 65,536 IP addresses are
               scanned. Proper host discovery is skipped as with the list scan,
               but instead of stopping and printing the target list, Nmap
               continues to perform requested functions as if each target IP is
               active. To skip ping scan and port scan, while still allowing NSE
               to run, use the two options -PN -sP together.
    
               For machines on a local ethernet network, ARP scanning will still
               be performed (unless --send-ip is specified) because Nmap needs MAC
               addresses to further scan target hosts. This option flag used to be
               P0 (uses zero), but was renamed to avoid confusion with protocol
               ping?s PO (uses the letter O) flag.
    
           -PS port list (TCP SYN Ping) .
               This option sends an empty TCP packet with the SYN flag set. The
               default destination port is 80 (configurable at compile time by
               changing DEFAULT_TCP_PROBE_PORT_SPEC in nmap.h).  Alternate ports
               can be specified as a parameter. The syntax is the same as for the
               -p except that port type specifiers like T: are not allowed.
               Examples are -PS22 and -PS22-25,80,113,1050,35000. Note that there
               can be no space between -PS and the port list. If multiple probes
               are specified they will be sent in parallel.
    
               The SYN flag suggests to the remote system that you are attempting
               to establish a connection. Normally the destination port will be
               closed, and a RST (reset) packet sent back. If the port happens to
               be open, the target will take the second step of a TCP
               three-way-handshake.  by responding with a SYN/ACK TCP packet. The
               machine running Nmap then tears down the nascent connection by
               responding with a RST rather than sending an ACK packet which would
               complete the three-way-handshake and establish a full connection.
               The RST packet is sent by the kernel of the machine running Nmap in
               response to the unexpected SYN/ACK, not by Nmap itself.
    
               Nmap does not care whether the port is open or closed. Either the
               RST or SYN/ACK response discussed previously tell Nmap that the
               host is available and responsive.
    
               On Unix boxes, only the privileged user root.  is generally able to
               send and receive raw TCP packets..  For unprivileged users, a
               workaround is automatically employed.  whereby the connect system
               call is initiated against each target port. This has the effect of
               sending a SYN packet to the target host, in an attempt to establish
               a connection. If connect returns with a quick success or an
               ECONNREFUSED failure, the underlying TCP stack must have received a
               SYN/ACK or RST and the host is marked available. If the connection
               attempt is left hanging until a timeout is reached, the host is
               marked as down. This workaround is also used for IPv6 connections,
               as raw IPv6 packet building support is not yet available in Nmap..
    
    
               The reason for offering both SYN and ACK ping probes is to maximize
               the chances of bypassing firewalls. Many administrators configure
               routers and other simple firewalls to block incoming SYN packets
               except for those destined for public services like the company web
               site or mail server. This prevents other incoming connections to
               the organization, while allowing users to make unobstructed
               outgoing connections to the Internet. This non-stateful approach
               takes up few resources on the firewall/router and is widely
               supported by hardware and software filters. The Linux
               Netfilter/iptables.  firewall software offers the --syn convenience
               option to implement this stateless approach. When stateless
               firewall rules such as this are in place, SYN ping probes (-PS) are
               likely to be blocked when sent to closed target ports. In such
               cases, the ACK probe shines as it cuts right through these rules.
    
               Another common type of firewall uses stateful rules that drop
               unexpected packets. This feature was initially found mostly on
               high-end firewalls, though it has become much more common over the
               years. The Linux Netfilter/iptables system supports this through
               the --state option, which categorizes packets based on connection
               state. A SYN probe is more likely to work against such a system, as
               unexpected ACK packets are generally recognized as bogus and
               dropped. A solution to this quandary is to send both SYN and ACK
               probes by specifying -PS and -PA.
    
           -PU port list (UDP Ping) .
               Another host discovery option is the UDP ping, which sends a UDP
               packet to the given ports. For most ports, the packet will be
               empty, though for a few a protocol-specific payload will be sent
               that is more likely to get a response..  See the file payload.cc.
               for exactly which ports have payloads. The --data-length.  option
               sends a fixed-length random payload for all ports.
    
               The port list takes the same format as with the previously
               discussed -PS and -PA options. If no ports are specified, the
               default is 40125. This default can be configured at compile-time by
               changing DEFAULT_UDP_PROBE_PORT_SPEC.  in nmap.h..  A highly
               uncommon port is used by default because sending to open ports is
               often undesirable for this particular scan type.
    
               Upon hitting a closed port on the target machine, the UDP probe
               should elicit an ICMP port unreachable packet in return. This
               signifies to Nmap that the machine is up and available. Many other
               types of ICMP errors, such as host/network unreachables or TTL
               exceeded are indicative of a down or unreachable host. A lack of
               response is also interpreted this way. If an open port is reached,
               most services simply ignore the empty packet and fail to return any
               response. This is why the default probe port is 40125, which is
               highly unlikely to be in use. A few services, such as the Character
               Generator (chargen) protocol, will respond to an empty UDP packet,
               and thus disclose to Nmap that the machine is available.
               Examples are -PY22 and -PY22,80,179,5060. Note that there can be no
               space between -PY and the port list. If multiple probes are
               specified they will be sent in parallel.
    
               The INIT chunk suggests to the remote system that you are
               attempting to establish an association. Normally the destination
               port will be closed, and an ABORT chunk will be sent back. If the
               port happens to be open, the target will take the second step of an
               SCTP four-way-handshake.  by responding with an INIT-ACK chunk. If
               the machine running Nmap has a functional SCTP stack, then it tears
               down the nascent association by responding with an ABORT chunk
               rather than sending a COOKIE-ECHO chunk which would be the next
               step in the four-way-handshake. The ABORT packet is sent by the
               kernel of the machine running Nmap in response to the unexpected
               INIT-ACK, not by Nmap itself.
    
               Nmap does not care whether the port is open or closed. Either the
               ABORT or INIT-ACK response discussed previously tell Nmap that the
               host is available and responsive.
    
               On Unix boxes, only the privileged user root.  is generally able to
               send and receive raw SCTP packets..  Using SCTP INIT Pings is
               currently not possible for unprivileged users..  The same
               limitation applies to IPv6, which is currently not supported for
               SCTP INIT Ping..
    
           -PE; -PP; -PM (ICMP Ping Types) .
               In addition to the unusual TCP, UDP and SCTP host discovery types
               discussed previously, Nmap can send the standard packets sent by
               the ubiquitous ping program. Nmap sends an ICMP type 8 (echo
               request) packet to the target IP addresses, expecting a type 0
               (echo reply) in return from available hosts..  Unfortunately for
               network explorers, many hosts and firewalls now block these
               packets, rather than responding as required by RFC 1122[2]. For
               this reason, ICMP-only scans are rarely reliable enough against
               unknown targets over the Internet. But for system administrators
               monitoring an internal network, they can be a practical and
               efficient approach. Use the -PE option to enable this echo request
               behavior.
    
               While echo request is the standard ICMP ping query, Nmap does not
               stop there. The ICMP standards (RFC 792[3].  and RFC 950[4].  "a
               host SHOULD NOT implement these messages". Timestamp and address
               mask queries can be sent with the -PP and -PM options,
               respectively. A timestamp reply (ICMP code 14) or address mask
               reply (code 18) discloses that the host is available. These two
               queries can be valuable when administrators specifically block echo
               request packets while forgetting that other ICMP queries can be
               used for the same purpose.
    
           -PO protocol list (IP Protocol Ping) .
               The newest host discovery option is the IP protocol ping, which
               same protocol as a probe, or ICMP protocol unreachable messages
               which signify that the given protocol isn?t supported on the
               destination host. Either type of response signifies that the target
               host is alive.
    
           -PR (ARP Ping) .
               One of the most common Nmap usage scenarios is to scan an ethernet
               LAN. On most LANs, especially those using private address ranges
               specified by RFC 1918[5], the vast majority of IP addresses are
               unused at any given time. When Nmap tries to send a raw IP packet
               such as an ICMP echo request, the operating system must determine
               the destination hardware (ARP) address corresponding to the target
               IP so that it can properly address the ethernet frame. This is
               often slow and problematic, since operating systems weren?t written
               with the expectation that they would need to do millions of ARP
               requests against unavailable hosts in a short time period.
    
               ARP scan puts Nmap and its optimized algorithms in charge of ARP
               requests. And if it gets a response back, Nmap doesn?t even need to
               worry about the IP-based ping packets since it already knows the
               host is up. This makes ARP scan much faster and more reliable than
               IP-based scans. So it is done by default when scanning ethernet
               hosts that Nmap detects are on a local ethernet network. Even if
               different ping types (such as -PE or -PS) are specified, Nmap uses
               ARP instead for any of the targets which are on the same LAN. If
               you absolutely don?t want to do an ARP scan, specify --send-ip.
    
           --traceroute (Trace path to host) .
               Traceroutes are performed post-scan using information from the scan
               results to determine the port and protocol most likely to reach the
               target. It works with all scan types except connect scans (-sT) and
               idle scans (-sI). All traces use Nmap?s dynamic timing model and
               are performed in parallel.
    
               Traceroute works by sending packets with a low TTL (time-to-live)
               in an attempt to elicit ICMP Time Exceeded messages from
               intermediate hops between the scanner and the target host. Standard
               traceroute implementations start with a TTL of 1 and increment the
               TTL until the destination host is reached. Nmap?s traceroute starts
               with a high TTL and then decrements the TTL until it reaches zero.
               Doing it backwards lets Nmap employ clever caching algorithms to
               speed up traces over multiple hosts. On average Nmap sends 5-10
               fewer packets per host, depending on network conditions. If a
               single subnet is being scanned (i.e. 192.168.0.0/24) Nmap may only
               have to send a single packet to most hosts.
    
           -n (No DNS resolution) .
               Tells Nmap to never do reverse DNS resolution on the active IP
               addresses it finds. Since DNS can be slow even with Nmap?s built-in
               parallel stub resolver, this option can slash scanning times.
    
           -R (DNS resolution for all targets) .
           --dns-servers server1[,server2[,...]]  (Servers to use for reverse DNS
           queries) .
               By default, Nmap determines your DNS servers (for rDNS resolution)
               from your resolv.conf file (Unix) or the Registry (Win32).
               Alternatively, you may use this option to specify alternate
               servers. This option is not honored if you are using --system-dns
               or an IPv6 scan. Using multiple DNS servers is often faster,
               especially if you choose authoritative servers for your target IP
               space. This option can also improve stealth, as your requests can
               be bounced off just about any recursive DNS server on the Internet.
    
               This option also comes in handy when scanning private networks.
               Sometimes only a few name servers provide proper rDNS information,
               and you may not even know where they are. You can scan the network
               for port 53 (perhaps with version detection), then try Nmap list
               scans (-sL) specifying each name server one at a time with
               --dns-servers until you find one which works.
    
    
    

    PORT SCANNING BASICS

           While Nmap has grown in functionality over the years, it began as an
           efficient port scanner, and that remains its core function. The simple
           command nmap target scans more than 1660 TCP ports on the host target.
           While many port scanners have traditionally lumped all ports into the
           open or closed states, Nmap is much more granular. It divides ports
           into six states: open, closed, filtered, unfiltered, open|filtered, or
           closed|filtered.
    
           These states are not intrinsic properties of the port itself, but
           describe how Nmap sees them. For example, an Nmap scan from the same
           network as the target may show port 135/tcp as open, while a scan at
           the same time with the same options from across the Internet might show
           that port as filtered.
    
           The six port states recognized by Nmap
    
               An application is actively accepting TCP connections, UDP datagrams
               or SCTP associations on this port. Finding these is often the
               primary goal of port scanning. Security-minded people know that
               each open port is an avenue for attack. Attackers and pen-testers
               want to exploit the open ports, while administrators try to close
               or protect them with firewalls without thwarting legitimate users.
               Open ports are also interesting for non-security scans because they
               show services available for use on the network.
    
               A closed port is accessible (it receives and responds to Nmap probe
               packets), but there is no application listening on it. They can be
               helpful in showing that a host is up on an IP address (host
               discovery, or ping scanning), and as part of OS detection. Because
               closed ports are reachable, it may be worth scanning later in case
               some open up. Administrators may want to consider blocking such
               ports with a firewall. Then they would appear in the filtered
               state, discussed next.
               unable to determine whether it is open or closed. Only the ACK
               scan, which is used to map firewall rulesets, classifies ports into
               this state. Scanning unfiltered ports with other scan types such as
               Window scan, SYN scan, or FIN scan, may help resolve whether the
               port is open.
    
               Nmap places ports in this state when it is unable to determine
               whether a port is open or filtered. This occurs for scan types in
               which open ports give no response. The lack of response could also
               mean that a packet filter dropped the probe or any response it
               elicited. So Nmap does not know for sure whether the port is open
               or being filtered. The UDP, IP protocol, FIN, NULL, and Xmas scans
               classify ports this way.
    
               This state is used when Nmap is unable to determine whether a port
               is closed or filtered. It is only used for the IP ID idle scan.
    
    
    

    PORT SCANNING TECHNIQUES

           As a novice performing automotive repair, I can struggle for hours
           trying to fit my rudimentary tools (hammer, duct tape, wrench, etc.) to
           the task at hand. When I fail miserably and tow my jalopy to a real
           mechanic, he invariably fishes around in a huge tool chest until
           pulling out the perfect gizmo which makes the job seem effortless. The
           art of port scanning is similar. Experts understand the dozens of scan
           techniques and choose the appropriate one (or combination) for a given
           task. Inexperienced users and script kiddies,.  on the other hand, try
           to solve every problem with the default SYN scan. Since Nmap is free,
           the only barrier to port scanning mastery is knowledge. That certainly
           beats the automotive world, where it may take great skill to determine
           that you need a strut spring compressor, then you still have to pay
           thousands of dollars for it.
    
           Most of the scan types are only available to privileged users..  This
           is because they send and receive raw packets,.  which requires root
           access on Unix systems. Using an administrator account on Windows is
           recommended, though Nmap sometimes works for unprivileged users on that
           platform when WinPcap has already been loaded into the OS. Requiring
           root privileges was a serious limitation when Nmap was released in
           1997, as many users only had access to shared shell accounts. Now, the
           world is different. Computers are cheaper, far more people have
           always-on direct Internet access, and desktop Unix systems (including
           Linux and Mac OS X) are prevalent. A Windows version of Nmap is now
           available, allowing it to run on even more desktops. For all these
           reasons, users have less need to run Nmap from limited shared shell
           accounts. This is fortunate, as the privileged options make Nmap far
           more powerful and flexible.
    
           While Nmap attempts to produce accurate results, keep in mind that all
           of its insights are based on packets returned by the target machines
           (or firewalls in front of them). Such hosts may be untrustworthy and
           send responses intended to confuse or mislead Nmap. Much more common
           are non-RFC-compliant hosts that do not respond as they should to Nmap
           unprivileged users can only execute connect and FTP bounce scans.
    
           -sS (TCP SYN scan) .
               SYN scan is the default and most popular scan option for good
               reasons. It can be performed quickly, scanning thousands of ports
               per second on a fast network not hampered by restrictive firewalls.
               SYN scan is relatively unobtrusive and stealthy, since it never
               completes TCP connections. It also works against any compliant TCP
               stack rather than depending on idiosyncrasies of specific platforms
               as Nmap?s FIN/NULL/Xmas, Maimon and idle scans do. It also allows
               clear, reliable differentiation between the open, closed, and
               filtered states.
    
               This technique is often referred to as half-open scanning, because
               you don?t open a full TCP connection. You send a SYN packet, as if
               you are going to open a real connection and then wait for a
               response. A SYN/ACK indicates the port is listening (open), while a
               RST (reset) is indicative of a non-listener. If no response is
               received after several retransmissions, the port is marked as
               filtered. The port is also marked filtered if an ICMP unreachable
               error (type 3, code 1, 2, 3, 9, 10, or 13) is received.
    
           -sT (TCP connect scan) .
               TCP connect scan is the default TCP scan type when SYN scan is not
               an option. This is the case when a user does not have raw packet
               privileges or is scanning IPv6 networks. Instead of writing raw
               packets as most other scan types do, Nmap asks the underlying
               operating system to establish a connection with the target machine
               and port by issuing the connect system call. This is the same
               high-level system call that web browsers, P2P clients, and most
               other network-enabled applications use to establish a connection.
               It is part of a programming interface known as the Berkeley Sockets
               API. Rather than read raw packet responses off the wire, Nmap uses
               this API to obtain status information on each connection attempt.
    
               When SYN scan is available, it is usually a better choice. Nmap has
               less control over the high level connect call than with raw
               packets, making it less efficient. The system call completes
               connections to open target ports rather than performing the
               half-open reset that SYN scan does. Not only does this take longer
               and require more packets to obtain the same information, but target
               machines are more likely to log the connection. A decent IDS will
               catch either, but most machines have no such alarm system. Many
               services on your average Unix system will add a note to syslog, and
               sometimes a cryptic error message, when Nmap connects and then
               closes the connection without sending data. Truly pathetic services
               crash when this happens, though that is uncommon. An administrator
               who sees a bunch of connection attempts in her logs from a single
               system should know that she has been connect scanned.
    
           -sU (UDP scans) .
               While most popular services on the Internet run over the TCP
               is sent, but for most ports the packet is empty..  The
               --data-length option can be used to send a fixed-length random
               payload to every port. If an ICMP port unreachable error (type 3,
               code 3) is returned, the port is closed. Other ICMP unreachable
               errors (type 3, codes 1, 2, 9, 10, or 13) mark the port as
               filtered. Occasionally, a service will respond with a UDP packet,
               proving that it is open. If no response is received after
               retransmissions, the port is classified as open|filtered. This
               means that the port could be open, or perhaps packet filters are
               blocking the communication. Version detection (-sV) can be used to
               help differentiate the truly open ports from the filtered ones.
    
               A big challenge with UDP scanning is doing it quickly. Open and
               filtered ports rarely send any response, leaving Nmap to time out
               and then conduct retransmissions just in case the probe or response
               were lost. Closed ports are often an even bigger problem. They
               usually send back an ICMP port unreachable error. But unlike the
               RST packets sent by closed TCP ports in response to a SYN or
               connect scan, many hosts rate limit.  ICMP port unreachable
               messages by default. Linux and Solaris are particularly strict
               about this. For example, the Linux 2.4.20 kernel limits destination
               unreachable messages to one per second (in net/ipv4/icmp.c).
    
               Nmap detects rate limiting and slows down accordingly to avoid
               flooding the network with useless packets that the target machine
               will drop. Unfortunately, a Linux-style limit of one packet per
               second makes a 65,536-port scan take more than 18 hours. Ideas for
               speeding your UDP scans up include scanning more hosts in parallel,
               doing a quick scan of just the popular ports first, scanning from
               behind the firewall, and using --host-timeout to skip slow hosts.
    
           -sY (SCTP INIT scan) .
    
               SCTP[7] is a relatively new alternative to the TCP and UDP
               protocols, combining most characteristics of TCP and UDP, and also
               adding new features like multi-homing and multi-streaming. It is
               mostly being used for SS7/SIGTRAN related services but has the
               potential to be used for other applications as well. SCTP INIT scan
               is the SCTP equivalent of a TCP SYN scan. It can be performed
               quickly, scanning thousands of ports per second on a fast network
               not hampered by restrictive firewalls. Like SYN scan, INIT scan is
               relatively unobtrusive and stealthy, since it never completes SCTP
               associations. It also allows clear, reliable differentiation
               between the open, closed, and filtered states.
    
               This technique is often referred to as half-open scanning, because
               you don?t open a full SCTP association. You send an INIT chunk, as
               if you are going to open a real association and then wait for a
               response. An INIT-ACK chunk indicates the port is listening (open),
               while an ABORT chunk is indicative of a non-listener. If no
               response is received after several retransmissions, the port is
               marked as filtered. The port is also marked filtered if an ICMP
               containing SYN, RST, or ACK bits will result in a returned RST if
               the port is closed and no response at all if the port is open. As
               long as none of those three bits are included, any combination of
               the other three (FIN, PSH, and URG) are OK. Nmap exploits this with
               three scan types:
    
               Null scan (-sN)
                   Does not set any bits (TCP flag header is 0)
    
               FIN scan (-sF)
                   Sets just the TCP FIN bit.
    
               Xmas scan (-sX)
                   Sets the FIN, PSH, and URG flags, lighting the packet up like a
                   Christmas tree.
    
               These three scan types are exactly the same in behavior except for
               the TCP flags set in probe packets. If a RST packet is received,
               the port is considered closed, while no response means it is
               open|filtered. The port is marked filtered if an ICMP unreachable
               error (type 3, code 1, 2, 3, 9, 10, or 13) is received.
    
               The key advantage to these scan types is that they can sneak
               through certain non-stateful firewalls and packet filtering
               routers. Another advantage is that these scan types are a little
               more stealthy than even a SYN scan. Don?t count on this though--most
               modern IDS products can be configured to detect them. The big
               downside is that not all systems follow RFC 793 to the letter. A
               number of systems send RST responses to the probes regardless of
               whether the port is open or not. This causes all of the ports to be
               labeled closed. Major operating systems that do this are Microsoft
               Windows, many Cisco devices, BSDI, and IBM OS/400. This scan does
               work against most Unix-based systems though. Another downside of
               these scans is that they can?t distinguish open ports from certain
               filtered ones, leaving you with the response open|filtered.
    
           -sA (TCP ACK scan) .
               This scan is different than the others discussed so far in that it
               never determines open (or even open|filtered) ports. It is used to
               map out firewall rulesets, determining whether they are stateful or
               not and which ports are filtered.
    
               The ACK scan probe packet has only the ACK flag set (unless you use
               --scanflags). When scanning unfiltered systems, open and closed
               ports will both return a RST packet. Nmap then labels them as
               unfiltered, meaning that they are reachable by the ACK packet, but
               whether they are open or closed is undetermined. Ports that don?t
               respond, or send certain ICMP error messages back (type 3, code 1,
               2, 3, 9, 10, or 13), are labeled filtered.
    
           -sW (TCP Window scan) .
               Window scan is exactly the same as ACK scan except that it exploits
               If most scanned ports are closed but a few common port numbers
               (such as 22, 25, 53) are filtered, the system is most likely
               susceptible. Occasionally, systems will even show the exact
               opposite behavior. If your scan shows 1000 open ports and three
               closed or filtered ports, then those three may very well be the
               truly open ones.
    
           -sM (TCP Maimon scan) .
               The Maimon scan is named after its discoverer, Uriel Maimon..  He
               described the technique in Phrack Magazine issue #49 (November
               1996)..  Nmap, which included this technique, was released two
               issues later. This technique is exactly the same as NULL, FIN, and
               Xmas scans, except that the probe is FIN/ACK. According to RFC
               793[8] (TCP), a RST packet should be generated in response to such
               a probe whether the port is open or closed. However, Uriel noticed
               that many BSD-derived systems simply drop the packet if the port is
               open.
    
           --scanflags (Custom TCP scan) .
               Truly advanced Nmap users need not limit themselves to the canned
               scan types offered. The --scanflags option allows you to design
               your own scan by specifying arbitrary TCP flags..  Let your
               creative juices flow, while evading intrusion detection systems.
               whose vendors simply paged through the Nmap man page adding
               specific rules!
    
               The --scanflags argument can be a numerical flag value such as 9
               (PSH and FIN), but using symbolic names is easier. Just mash
               together any combination of URG, ACK, PSH, RST, SYN, and FIN. For
               example, --scanflags URGACKPSHRSTSYNFIN sets everything, though
               it?s not very useful for scanning. The order these are specified in
               is irrelevant.
    
               In addition to specifying the desired flags, you can specify a TCP
               scan type (such as -sA or -sF). That base type tells Nmap how to
               interpret responses. For example, a SYN scan considers no-response
               to indicate a filtered port, while a FIN scan treats the same as
               open|filtered. Nmap will behave the same way it does for the base
               scan type, except that it will use the TCP flags you specify
               instead. If you don?t specify a base type, SYN scan is used.
    
           -sZ (SCTP COOKIE ECHO scan) .
               SCTP COOKIE ECHO scan is a more advanced SCTP scan. It takes
               advantage of the fact that SCTP implementations should silently
               drop packets containing COOKIE ECHO chunks on open ports, but send
               an ABORT if the port is closed. The advantage of this scan type is
               that it is not as obvious a port scan than an INIT scan. Also,
               there may be non-stateful firewall rulesets blocking INIT chunks,
               but not COOKIE ECHO chunks. Don?t be fooled into thinking that this
               will make a port scan invisible; a good IDS will be able to detect
               SCTP COOKIE ECHO scans too. The downside is that SCTP COOKIE ECHO
               scans cannot differentiate between open and filtered ports, leaving
               Besides being extraordinarily stealthy (due to its blind nature),
               this scan type permits mapping out IP-based trust relationships
               between machines. The port listing shows open ports from the
               perspective of the zombie host.  So you can try scanning a target
               using various zombies that you think might be trusted.  (via
               router/packet filter rules).
    
               You can add a colon followed by a port number to the zombie host if
               you wish to probe a particular port on the zombie for IP ID
               changes. Otherwise Nmap will use the port it uses by default for
               TCP pings (80).
    
           -sO (IP protocol scan) .
               IP protocol scan allows you to determine which IP protocols (TCP,
               ICMP, IGMP, etc.) are supported by target machines. This isn?t
               technically a port scan, since it cycles through IP protocol
               numbers rather than TCP or UDP port numbers. Yet it still uses the
               -p option to select scanned protocol numbers, reports its results
               within the normal port table format, and even uses the same
               underlying scan engine as the true port scanning methods. So it is
               close enough to a port scan that it belongs here.
    
               Besides being useful in its own right, protocol scan demonstrates
               the power of open-source software. While the fundamental idea is
               pretty simple, I had not thought to add it nor received any
               requests for such functionality. Then in the summer of 2000,
               Gerhard Rieger.  conceived the idea, wrote an excellent patch
               implementing it, and sent it to the nmap-hackers mailing list..  I
               incorporated that patch into the Nmap tree and released a new
               version the next day. Few pieces of commercial software have users
               enthusiastic enough to design and contribute their own
               improvements!
    
               Protocol scan works in a similar fashion to UDP scan. Instead of
               iterating through the port number field of a UDP packet, it sends
               IP packet headers and iterates through the eight-bit IP protocol
               field. The headers are usually empty, containing no data and not
               even the proper header for the claimed protocol. The exceptions are
               TCP, UDP, ICMP, SCTP, and IGMP. A proper protocol header for those
               is included since some systems won?t send them otherwise and
               because Nmap already has functions to create them. Instead of
               watching for ICMP port unreachable messages, protocol scan is on
               the lookout for ICMP protocol unreachable messages. If Nmap
               receives any response in any protocol from the target host, Nmap
               marks that protocol as open. An ICMP protocol unreachable error
               (type 3, code 2) causes the protocol to be marked as closed Other
               ICMP unreachable errors (type 3, code 1, 3, 9, 10, or 13) cause the
               protocol to be marked filtered (though they prove that ICMP is open
               at the same time). If no response is received after
               retransmissions, the protocol is marked open|filtered
    
           -b FTP relay host (FTP bounce scan) .
               URL, you may omit username:password, in which case anonymous login
               credentials (user: anonymous password:-wwwuser@) are used. The port
               number (and preceding colon) may be omitted as well, in which case
               the default FTP port (21) on server is used.
    
               This vulnerability was widespread in 1997 when Nmap was released,
               but has largely been fixed. Vulnerable servers are still around, so
               it is worth trying when all else fails. If bypassing a firewall is
               your goal, scan the target network for open port 21 (or even for
               any FTP services if you scan all ports with version detection),
               then try a bounce scan using each. Nmap will tell you whether the
               host is vulnerable or not. If you are just trying to cover your
               tracks, you don?t need to (and, in fact, shouldn?t) limit yourself
               to hosts on the target network. Before you go scanning random
               Internet addresses for vulnerable FTP servers, consider that
               sysadmins may not appreciate you abusing their servers in this way.
    
    
    

    PORT SPECIFICATION AND SCAN ORDER

           In addition to all of the scan methods discussed previously, Nmap
           offers options for specifying which ports are scanned and whether the
           scan order is randomized or sequential. By default, Nmap scans the most
           common 1,000 ports for each protocol.
    
           -p port ranges (Only scan specified ports) .
               This option specifies which ports you want to scan and overrides
               the default. Individual port numbers are OK, as are ranges
               separated by a hyphen (e.g.  1-1023). The beginning and/or end
               values of a range may be omitted, causing Nmap to use 1 and 65535,
               respectively. So you can specify -p- to scan ports from 1 through
               65535. Scanning port zero.  is allowed if you specify it
               explicitly. For IP protocol scanning (-sO), this option specifies
               the protocol numbers you wish to scan for (0-255).
    
               When scanning both TCP and UDP ports, you can specify a particular
               protocol by preceding the port numbers by T: or U:. The qualifier
               lasts until you specify another qualifier. For example, the
               argument -p U:53,111,137,T:21-25,80,139,8080 would scan UDP ports
               53, 111,and 137, as well as the listed TCP ports. Note that to scan
               both UDP and TCP, you have to specify -sU and at least one TCP scan
               type (such as -sS, -sF, or -sT). If no protocol qualifier is given,
               the port numbers are added to all protocol lists.  Ports can also
               be specified by name according to what the port is referred to in
               the nmap-services. You can even use the wildcards * and ? with the
               names. For example, to scan FTP and all ports whose names begin
               with "http", use -p ftp,http*. Be careful about shell expansions
               and quote the argument to -p if unsure.
    
               Ranges of ports can be surrounded by square brackets to indicate
               ports inside that range that appear in nmap-services. For example,
               the following will scan all ports in nmap-services equal to or
               below 1024: -p [-1024]. Be careful with shell expansions and quote
               the argument to -p if unsure.
               By default, Nmap randomizes the scanned port order (except that
               certain commonly accessible ports are moved near the beginning for
               efficiency reasons). This randomization is normally desirable, but
               you can specify -r for sequential (sorted from lowest to highest)
               port scanning instead.
    
           --port-ratio <decimal number between 0 and 1>
               Scans all ports in nmap-services file with a ratio greater than the
               number specified as the argument.
    
           --top-ports <integer of 1 or greater>
               Scans the N highest-ratio ports found in nmap-services file.
    
    
    

    SERVICE AND VERSION DETECTION

           Point Nmap at a remote machine and it might tell you that ports 25/tcp,
           80/tcp, and 53/udp are open. Using its nmap-services.  database of
           about 2,200 well-known services,.  Nmap would report that those ports
           probably correspond to a mail server (SMTP), web server (HTTP), and
           name server (DNS) respectively. This lookup is usually accurate--the
           vast majority of daemons listening on TCP port 25 are, in fact, mail
           servers. However, you should not bet your security on this! People can
           and do run services on strange ports..
    
           Even if Nmap is right, and the hypothetical server above is running
           SMTP, HTTP, and DNS servers, that is not a lot of information. When
           doing vulnerability assessments (or even simple network inventories) of
           your companies or clients, you really want to know which mail and DNS
           servers and versions are running. Having an accurate version number
           helps dramatically in determining which exploits a server is vulnerable
           to. Version detection helps you obtain this information.
    
           After TCP and/or UDP ports are discovered using one of the other scan
           methods, version detection interrogates those ports to determine more
           about what is actually running. The nmap-service-probes.  database
           contains probes for querying various services and match expressions to
           recognize and parse responses. Nmap tries to determine the service
           protocol (e.g. FTP, SSH, Telnet, HTTP), the application name (e.g. ISC
           BIND, Apache httpd, Solaris telnetd), the version number, hostname,
           device type (e.g. printer, router), the OS family (e.g. Windows, Linux)
           and sometimes miscellaneous details like whether an X server is open to
           connections, the SSH protocol version, or the KaZaA user name). Of
           course, most services don?t provide all of this information. If Nmap
           was compiled with OpenSSL support, it will connect to SSL servers to
           deduce the service listening behind that encryption layer..  When RPC
           services are discovered, the Nmap RPC grinder.  (-sR).  is
           automatically used to determine the RPC program and version numbers.
           Some UDP ports are left in the open|filtered state after a UDP port
           scan is unable to determine whether the port is open or filtered.
           Version detection will try to elicit a response from these ports (just
           as it does with open ports), and change the state to open if it
           succeeds.  open|filtered TCP ports are treated the same way. Note that
           the Nmap -A option enables version detection among other things.  A
               Enables version detection, as discussed above. Alternatively, you
               can use -A, which enables version detection among other things.
    
           --allports (Don?t exclude any ports from version detection) .
               By default, Nmap version detection skips TCP port 9100 because some
               printers simply print anything sent to that port, leading to dozens
               of pages of HTTP GET requests, binary SSL session requests, etc.
               This behavior can be changed by modifying or removing the Exclude
               directive in nmap-service-probes, or you can specify --allports to
               scan all ports regardless of any Exclude directive.
    
           --version-intensity intensity (Set version scan intensity) .
               When performing a version scan (-sV), Nmap sends a series of
               probes, each of which is assigned a rarity value between one and
               nine. The lower-numbered probes are effective against a wide
               variety of common services, while the higher numbered ones are
               rarely useful. The intensity level specifies which probes should be
               applied. The higher the number, the more likely it is the service
               will be correctly identified. However, high intensity scans take
               longer. The intensity must be between 0 and 9.  The default is 7.
               When a probe is registered to the target port via the
               nmap-service-probes ports directive, that probe is tried regardless
               of intensity level. This ensures that the DNS probes will always be
               attempted against any open port 53, the SSL probe will be done
               against 443, etc.
    
           --version-light (Enable light mode) .
               This is a convenience alias for --version-intensity 2. This light
               mode makes version scanning much faster, but it is slightly less
               likely to identify services.
    
           --version-all (Try every single probe) .
               An alias for --version-intensity 9, ensuring that every single
               probe is attempted against each port.
    
           --version-trace (Trace version scan activity) .
               This causes Nmap to print out extensive debugging info about what
               version scanning is doing. It is a subset of what you get with
               --packet-trace.
    
           -sR (RPC scan) .
               This method works in conjunction with the various port scan methods
               of Nmap. It takes all the TCP/UDP ports found open and floods them
               with SunRPC program NULL commands in an attempt to determine
               whether they are RPC ports, and if so, what program and version
               number they serve up. Thus you can effectively obtain the same info
               as rpcinfo -p even if the target?s portmapper is behind a firewall
               (or protected by TCP wrappers). Decoys do not currently work with
               RPC scan..  This is automatically enabled as part of version scan
               (-sV) if you request that. As version detection includes this and
               is much more comprehensive, -sR is rarely needed.
    
           (e.g. at least one open port and one closed port were found), Nmap will
           provide a URL you can use to submit the fingerprint if you know (for
           sure) the OS running on the machine. By doing this you contribute to
           the pool of operating systems known to Nmap and thus it will be more
           accurate for everyone.
    
           OS detection enables some other tests which make use of information
           that is gathered during the process anyway. One of these is TCP
           Sequence Predictability Classification. This measures approximately how
           hard it is to establish a forged TCP connection against the remote
           host. It is useful for exploiting source-IP based trust relationships
           (rlogin, firewall filters, etc) or for hiding the source of an attack.
           This sort of spoofing is rarely performed any more, but many machines
           are still vulnerable to it. The actual difficulty number is based on
           statistical sampling and may fluctuate. It is generally better to use
           the English classification such as "worthy challenge" or "trivial
           joke". This is only reported in normal output in verbose (-v) mode.
           When verbose mode is enabled along with -O, IP ID sequence generation
           is also reported. Most machines are in the "incremental" class, which
           means that they increment the ID field in the IP header for each packet
           they send. This makes them vulnerable to several advanced information
           gathering and spoofing attacks.
    
           Another bit of extra information enabled by OS detection is a guess at
           a target?s uptime. This uses the TCP timestamp option (RFC 1323[10]) to
           guess when a machine was last rebooted. The guess can be inaccurate due
           to the timestamp counter not being initialized to zero or the counter
           overflowing and wrapping around, so it is printed only in verbose mode.
    
           A paper documenting the workings, usage, and customization of OS
           detection is available at http://nmap.org/book/osdetect.html.
    
           OS detection is enabled and controlled with the following options:
    
           -O (Enable OS detection) .
               Enables OS detection, as discussed above. Alternatively, you can
               use -A to enable OS detection along with other things.
    
           --osscan-limit (Limit OS detection to promising targets) .
               OS detection is far more effective if at least one open and one
               closed TCP port are found. Set this option and Nmap will not even
               try OS detection against hosts that do not meet this criteria. This
               can save substantial time, particularly on -PN scans against many
               hosts. It only matters when OS detection is requested with -O or
               -A.
    
           --osscan-guess; --fuzzy (Guess OS detection results) .
               When Nmap is unable to detect a perfect OS match, it sometimes
               offers up near-matches as possibilities. The match has to be very
               close for Nmap to do this by default. Either of these (equivalent)
               options make Nmap guess more aggressively. Nmap will still tell you
               the Nmap OS database.
    
    
    

    NMAP SCRIPTING ENGINE (NSE)

           The Nmap Scripting Engine (NSE) is one of Nmap?s most powerful and
           flexible features. It allows users to write (and share) simple scripts
           (using the Lua programming language[11],
    
           Tasks we had in mind when creating the system include network
           discovery, more sophisticated version detection, vulnerability
           detection. NSE can even be used for vulnerability exploitation.
    
           To reflect those different uses and to simplify the choice of which
           scripts to run, each script contains a field associating it with one or
           more categories. Currently defined categories are safe, intrusive,
           malware, version, discovery, vuln, auth, and default. These are all
           described at http://nmap.org/book/nse-usage.html#nse-categories.
    
           Scripts are not run in a sandbox and thus could accidentally or
           maliciously damage your system or invade your privacy. Never run
           scripts from third parties unless you trust the authors or have
           carefully audited the scripts yourself.
    
           The Nmap Scripting Engine is described in detail at
           http://nmap.org/book/nse.html
    
           and is controlled by the following options:
    
           -sC .
               Performs a script scan using the default set of scripts. It is
               equivalent to --script=default. Some of the scripts in this
               category are considered intrusive and should not be run against a
               target network without permission.
    
           --script filename|category|directory|expression|all[,...] .
               Runs a script scan using the comma-separated list of filenames,
               script categories, and directories. Each element in the list may
               also be a Boolean expression describing a more complex set of
               scripts. Each element is interpreted first as an expression, then
               as a category, and finally as a file or directory name. The special
               argument all makes every script in Nmap?s script database eligible
               to run. The all argument should be used with caution as NSE may
               contain dangerous scripts including exploits, brute force
               authentication crackers, and denial of service attacks.
    
               File and directory names may be relative or absolute. Absolute
               names are used directly. Relative paths are looked for in the
               following places until found:
                   --datadir
                   $NMAPDIR
                   ~/.nmap (not searched on Windows)
                   NMAPDATADIR
                   the current directory
    
               nmap --script "http-*"
                   Loads all scripts whose name starts with http-, such as
                   http-auth.nse and http-open-proxy.nse. The argument to --script
                   had to be in quotes to protect the wildcard from the shell.
    
               More complicated script selection can be done using the and, or,
               and not operators to build Boolean expressions. The operators have
               the same precedence[12] as in Lua: not is the highest, followed by
               and and then or. You can alter precedence by using parentheses.
               Because expressions contain space characters it is necessary to
               quote them.
    
               nmap --script "not intrusive"
                   Loads every script except for those in the intrusive category.
    
               nmap --script "default or safe"
                   This is functionally equivalent to nmap --script
                   "default,safe". It loads all scripts that are in the default
                   category or the safe category or both.
    
               nmap --script "default and safe"
                   Loads those scripts that are in both the default and safe
                   categories.
    
               nmap --script "(default or safe or intrusive) and not http-*"
                   Loads scripts in the default, safe, or intrusive categories,
                   except for those whose names start with http-.
    
           --script-args name1=value1,name2={name3=value3},name4={value4,value5} .
               Lets you provide arguments to NSE scripts. Arguments are a
               comma-separated list of name=value pairs. Names and values may be
               strings not containing whitespace or the characters '{', '}', '=',
               or ','. To include one of these characters in a string, enclose the
               string in single or double quotes. Within a quoted string, '\'
               escapes a quote. A backslash is only used to escape quotation marks
               in this special case; in all other cases a backslash is interpreted
               literally. Values may also be tables enclosed in {}, just as in
               Lua. A table may contain simple string values or more name-value
               pairs, including nested tables. An example of script arguments:
               --script-args
               auth={user=foo,pass=?,{}=bar?},userdb=C:\Path\To\File. The online
               NSE Documentation Portal at http://nmap.org/nsedoc/ lists the
               arguments that each script accepts.
    
           --script-trace .
               This option does what --packet-trace does, just one ISO layer
               higher. If this option is specified all incoming and outgoing
               communication performed by a script is printed. The displayed
               information includes the communication protocol, the source, the
               target and the transmitted data. If more than 5% of all transmitted
               data is not printable, then the trace output is in a hex dump
    
           but adds up when you are scanning hundreds or thousands of hosts.
           Moreover, certain scan options such as UDP scanning and version
           detection can increase scan times substantially. So can certain
           firewall configurations, particularly response rate limiting. While
           Nmap utilizes parallelism and many advanced algorithms to accelerate
           these scans, the user has ultimate control over how Nmap runs. Expert
           users carefully craft Nmap commands to obtain only the information they
           care about while meeting their time constraints.
    
           Techniques for improving scan times include omitting non-critical
           tests, and upgrading to the latest version of Nmap (performance
           enhancements are made frequently). Optimizing timing parameters can
           also make a substantial difference. Those options are listed below.
    
           Some options accept a time parameter. This is specified in milliseconds
           by default, though you can append 's', 'm', or 'h' to the value to
           specify seconds, minutes, or hours. So the --host-timeout arguments
           900000, 900s, and 15m all do the same thing.
    
           --min-hostgroup numhosts; --max-hostgroup numhosts (Adjust parallel
           scan group sizes) .
               Nmap has the ability to port scan or version scan multiple hosts in
               parallel. Nmap does this by dividing the target IP space into
               groups and then scanning one group at a time. In general, larger
               groups are more efficient. The downside is that host results can?t
               be provided until the whole group is finished. So if Nmap started
               out with a group size of 50, the user would not receive any reports
               (except for the updates offered in verbose mode) until the first 50
               hosts are completed.
    
               By default, Nmap takes a compromise approach to this conflict. It
               starts out with a group size as low as five so the first results
               come quickly and then increases the groupsize to as high as 1024.
               The exact default numbers depend on the options given. For
               efficiency reasons, Nmap uses larger group sizes for UDP or
               few-port TCP scans.
    
               When a maximum group size is specified with --max-hostgroup, Nmap
               will never exceed that size. Specify a minimum size with
               --min-hostgroup and Nmap will try to keep group sizes above that
               level. Nmap may have to use smaller groups than you specify if
               there are not enough target hosts left on a given interface to
               fulfill the specified minimum. Both may be set to keep the group
               size within a specific range, though this is rarely desired.
    
               These options do not have an effect during the host discovery phase
               of a scan. This includes plain ping scans (-sP). Host discovery
               always works in large groups of hosts to improve speed and
               accuracy.
    
               The primary use of these options is to specify a large minimum
               group size so that the full scan runs more quickly. A common choice
               variable. By default, the ideal parallelism can drop to one if the
               network proves unreliable and rise to several hundred in perfect
               conditions.
    
               The most common usage is to set --min-parallelism to a number
               higher than one to speed up scans of poorly performing hosts or
               networks. This is a risky option to play with, as setting it too
               high may affect accuracy. Setting this also reduces Nmap?s ability
               to control parallelism dynamically based on network conditions. A
               value of ten might be reasonable, though I only adjust this value
               as a last resort.
    
               The --max-parallelism option is sometimes set to one to prevent
               Nmap from sending more than one probe at a time to hosts. The
               --scan-delay option, discussed later, is another way to do this.
    
           --min-rtt-timeout time, --max-rtt-timeout time, --initial-rtt-timeout
           time (Adjust probe timeouts) .
               Nmap maintains a running timeout value for determining how long it
               will wait for a probe response before giving up or retransmitting
               the probe. This is calculated based on the response times of
               previous probes.
    
               If the network latency shows itself to be significant and variable,
               this timeout can grow to several seconds. It also starts at a
               conservative (high) level and may stay that way for a while when
               Nmap scans unresponsive hosts.
    
               Specifying a lower --max-rtt-timeout and --initial-rtt-timeout than
               the defaults can cut scan times significantly. This is particularly
               true for pingless (-PN) scans, and those against heavily filtered
               networks. Don?t get too aggressive though. The scan can end up
               taking longer if you specify such a low value that many probes are
               timing out and retransmitting while the response is in transit.
    
               If all the hosts are on a local network, 100 milliseconds is a
               reasonable aggressive --max-rtt-timeout value. If routing is
               involved, ping a host on the network first with the ICMP ping
               utility, or with a custom packet crafter such as hping2.  that is
               more likely to get through a firewall. Look at the maximum round
               trip time out of ten packets or so. You might want to double that
               for the --initial-rtt-timeout and triple or quadruple it for the
               --max-rtt-timeout. I generally do not set the maximum RTT below
               100 ms, no matter what the ping times are. Nor do I exceed 1000 ms.
    
               --min-rtt-timeout is a rarely used option that could be useful when
               a network is so unreliable that even Nmap?s default is too
               aggressive. Since Nmap only reduces the timeout down to the minimum
               when the network seems to be reliable, this need is unusual and
               should be reported as a bug to the nmap-dev mailing list..
    
           --max-retries numtries (Specify the maximum number of port scan probe
               The default (with no -T template) is to allow ten retransmissions.
               If a network seems reliable and the target hosts aren?t rate
               limiting, Nmap usually only does one retransmission. So most target
               scans aren?t even affected by dropping --max-retries to a low value
               such as three. Such values can substantially speed scans of slow
               (rate limited) hosts. You usually lose some information when Nmap
               gives up on ports early, though that may be preferable to letting
               the --host-timeout expire and losing all information about the
               target.
    
           --host-timeout time (Give up on slow target hosts) .
               Some hosts simply take a long time to scan. This may be due to
               poorly performing or unreliable networking hardware or software,
               packet rate limiting, or a restrictive firewall. The slowest few
               percent of the scanned hosts can eat up a majority of the scan
               time. Sometimes it is best to cut your losses and skip those hosts
               initially. Specify --host-timeout with the maximum amount of time
               you are willing to wait. For example, specify 30m to ensure that
               Nmap doesn?t waste more than half an hour on a single host. Note
               that Nmap may be scanning other hosts at the same time during that
               half an hour, so it isn?t a complete loss. A host that times out is
               skipped. No port table, OS detection, or version detection results
               are printed for that host.
    
           --scan-delay time; --max-scan-delay time (Adjust delay between probes)
           .
               This option causes Nmap to wait at least the given amount of time
               between each probe it sends to a given host. This is particularly
               useful in the case of rate limiting..  Solaris machines (among many
               others) will usually respond to UDP scan probe packets with only
               one ICMP message per second. Any more than that sent by Nmap will
               be wasteful. A --scan-delay of 1s will keep Nmap at that slow rate.
               Nmap tries to detect rate limiting and adjust the scan delay
               accordingly, but it doesn?t hurt to specify it explicitly if you
               already know what rate works best.
    
               When Nmap adjusts the scan delay upward to cope with rate limiting,
               the scan slows down dramatically. The --max-scan-delay option
               specifies the largest delay that Nmap will allow. A low
               --max-scan-delay can speed up Nmap, but it is risky. Setting this
               value too low can lead to wasteful packet retransmissions and
               possible missed ports when the target implements strict rate
               limiting.
    
               Another use of --scan-delay is to evade threshold based intrusion
               detection and prevention systems (IDS/IPS)..
    
           --min-rate number; --max-rate number (Directly control the scanning
           rate) .
               Nmap?s dynamic timing does a good job of finding an appropriate
               speed at which to scan. Sometimes, however, you may happen to know
               an appropriate scanning rate for a network, or you may have to
               maximum. Use --max-rate 100, for example, to limit sending to 100
               packets per second on a fast network. Use --max-rate 0.1 for a slow
               scan of one packet every ten seconds. Use --min-rate and --max-rate
               together to keep the rate inside a certain range.
    
               These two options are global, affecting an entire scan, not
               individual hosts. They only affect port scans and host discovery
               scans. Other features like OS detection implement their own timing.
    
               There are two conditions when the actual scanning rate may fall
               below the requested minimum. The first is if the minimum is faster
               than the fastest rate at which Nmap can send, which is dependent on
               hardware. In this case Nmap will simply send packets as fast as
               possible, but be aware that such high rates are likely to cause a
               loss of accuracy. The second case is when Nmap has nothing to send,
               for example at the end of a scan when the last probes have been
               sent and Nmap is waiting for them to time out or be responded to.
               It?s normal to see the scanning rate drop at the end of a scan or
               in between hostgroups. The sending rate may temporarily exceed the
               maximum to make up for unpredictable delays, but on average the
               rate will stay at or below the maximum.
    
               Specifying a minimum rate should be done with care. Scanning faster
               than a network can support may lead to a loss of accuracy. In some
               cases, using a faster rate can make a scan take longer than it
               would with a slower rate. This is because Nmap?s
    
               adaptive retransmission algorithms will detect the network
               congestion caused by an excessive scanning rate and increase the
               number of retransmissions in order to improve accuracy. So even
               though packets are sent at a higher rate, more packets are sent
               overall. Cap the number of retransmissions with the --max-retries
               option if you need to set an upper limit on total scan time.
    
           --defeat-rst-ratelimit .
               Many hosts have long used rate limiting.  to reduce the number of
               ICMP error messages (such as port-unreachable errors) they send.
               Some systems now apply similar rate limits to the RST (reset)
               packets they generate. This can slow Nmap down dramatically as it
               adjusts its timing to reflect those rate limits. You can tell Nmap
               to ignore those rate limits (for port scans such as SYN scan which
               don?t treat non-responsive ports as open) by specifying
               --defeat-rst-ratelimit.
    
               Using this option can reduce accuracy, as some ports will appear
               non-responsive because Nmap didn?t wait long enough for a
               rate-limited RST response. With a SYN scan, the non-response
               results in the port being labeled filtered rather than the closed
               state we see when RST packets are received. This option is useful
               when you only care about open ports, and distinguishing between
               closed and filtered ports isn?t worth the extra time.
    
               Finally insane mode.  assumes that you are on an extraordinarily
               fast network or are willing to sacrifice some accuracy for speed.
    
               These templates allow the user to specify how aggressive they wish
               to be, while leaving Nmap to pick the exact timing values. The
               templates also make some minor speed adjustments for which
               fine-grained control options do not currently exist. For example,
               -T4.  prohibits the dynamic scan delay from exceeding 10 ms for TCP
               ports and -T5 caps that value at 5 ms. Templates can be used in
               combination with fine-grained controls, and the fine-grained
               controls will you specify will take precedence over the timing
               template default for that parameter. I recommend using -T4 when
               scanning reasonably modern and reliable networks. Keep that option
               even when you add fine-grained controls so that you benefit from
               those extra minor optimizations that it enables.
    
               If you are on a decent broadband or ethernet connection, I would
               recommend always using -T4. Some people love -T5 though it is too
               aggressive for my taste. People sometimes specify -T2 because they
               think it is less likely to crash hosts or because they consider
               themselves to be polite in general. They often don?t realize just
               how slow -T polite.  really is. Their scan may take ten times
               longer than a default scan. Machine crashes and bandwidth problems
               are rare with the default timing options (-T3) and so I normally
               recommend that for cautious scanners. Omitting version detection is
               far more effective than playing with timing values at reducing
               these problems.
    
               While -T0.  and -T1.  may be useful for avoiding IDS alerts, they
               will take an extraordinarily long time to scan thousands of
               machines or ports. For such a long scan, you may prefer to set the
               exact timing values you need rather than rely on the canned -T0 and
               -T1 values.
    
               The main effects of T0 are serializing the scan so only one port is
               scanned at a time, and waiting five minutes between sending each
               probe.  T1 and T2 are similar but they only wait 15 seconds and 0.4
               seconds, respectively, between probes.  T3 is Nmap?s default
               behavior, which includes parallelization..  -T4 does the equivalent
               of --max-rtt-timeout 1250 --initial-rtt-timeout 500 --max-retries 6
               and sets the maximum TCP scan delay to 10 milliseconds.  T5 does
               the equivalent of --max-rtt-timeout 300 --min-rtt-timeout 50
               --initial-rtt-timeout 250 --max-retries 2 --host-timeout 15m as
               well as setting the maximum TCP scan delay to 5 ms.
    
    
    

    FIREWALL/IDS EVASION AND SPOOFING

           Many Internet pioneers envisioned a global open network with a
           universal IP address space allowing virtual connections between any two
           nodes. This allows hosts to act as true peers, serving and retrieving
           information from each other. People could access all of their home
           systems from work, changing the climate control settings or unlocking
           the doors for early guests. This vision of universal connectivity has
           One of the best methods of understanding your network security posture
           is to try to defeat it. Place yourself in the mind-set of an attacker,
           and deploy techniques from this section against your networks. Launch
           an FTP bounce scan, idle scan, fragmentation attack, or try to tunnel
           through one of your own proxies.
    
           In addition to restricting network activity, companies are increasingly
           monitoring traffic with intrusion detection systems (IDS). All of the
           major IDSs ship with rules designed to detect Nmap scans because scans
           are sometimes a precursor to attacks. Many of these products have
           recently morphed into intrusion prevention systems (IPS).  that
           actively block traffic deemed malicious. Unfortunately for network
           administrators and IDS vendors, reliably detecting bad intentions by
           analyzing packet data is a tough problem. Attackers with patience,
           skill, and the help of certain Nmap options can usually pass by IDSs
           undetected. Meanwhile, administrators must cope with large numbers of
           false positive results where innocent activity is misdiagnosed and
           alerted on or blocked.
    
           Occasionally people suggest that Nmap should not offer features for
           evading firewall rules or sneaking past IDSs. They argue that these
           features are just as likely to be misused by attackers as used by
           administrators to enhance security. The problem with this logic is that
           these methods would still be used by attackers, who would just find
           other tools or patch the functionality into Nmap. Meanwhile,
           administrators would find it that much harder to do their jobs.
           Deploying only modern, patched FTP servers is a far more powerful
           defense than trying to prevent the distribution of tools implementing
           the FTP bounce attack.
    
           There is no magic bullet (or Nmap option) for detecting and subverting
           firewalls and IDS systems. It takes skill and experience. A tutorial is
           beyond the scope of this reference guide, which only lists the relevant
           options and describes what they do.
    
           -f (fragment packets); --mtu (using the specified MTU) .
               The -f option causes the requested scan (including ping scans) to
               use tiny fragmented IP packets. The idea is to split up the TCP
               header over several packets to make it harder for packet filters,
               intrusion detection systems, and other annoyances to detect what
               you are doing. Be careful with this! Some programs have trouble
               handling these tiny packets. The old-school sniffer named Sniffit
               segmentation faulted immediately upon receiving the first fragment.
               Specify this option once, and Nmap splits the packets into eight
               bytes or less after the IP header. So a 20-byte TCP header would be
               split into three packets. Two with eight bytes of the TCP header,
               and one with the final four. Of course each fragment also has an IP
               header. Specify -f again to use 16 bytes per fragment (reducing the
               number of fragments)..  Or you can specify your own offset size
               with the --mtu option. Don?t also specify -f if you use --mtu. The
               offset must be a multiple of eight. While fragmented packets won?t
               get by packet filters and firewalls that queue all IP fragments,
               and the Nmap Scripting Engine generally don?t support fragmentation
               because they rely on your host?s TCP stack to communicate with
               target services.
    
           -D decoy1[,decoy2][,ME][,...] (Cloak a scan with decoys) .
               Causes a decoy scan to be performed, which makes it appear to the
               remote host that the host(s) you specify as decoys are scanning the
               target network too. Thus their IDS might report 5-10 port scans
               from unique IP addresses, but they won?t know which IP was scanning
               them and which were innocent decoys. While this can be defeated
               through router path tracing, response-dropping, and other active
               mechanisms, it is generally an effective technique for hiding your
               IP address.
    
               Separate each decoy host with commas, and you can optionally use
               ME.  as one of the decoys to represent the position for your real
               IP address. If you put ME in the sixth position or later, some
               common port scan detectors (such as Solar Designer?s.  excellent
               Scanlogd).  are unlikely to show your IP address at all. If you
               don?t use ME, Nmap will put you in a random position. You can also
               use RND.  to generate a random, non-reserved IP address, or
               RND:number to generate number addresses.
    
               Note that the hosts you use as decoys should be up or you might
               accidentally SYN flood your targets. Also it will be pretty easy to
               determine which host is scanning if only one is actually up on the
               network. You might want to use IP addresses instead of names (so
               the decoy networks don?t see you in their nameserver logs).
    
               Decoys are used both in the initial ping scan (using ICMP, SYN,
               ACK, or whatever) and during the actual port scanning phase. Decoys
               are also used during remote OS detection (-O). Decoys do not work
               with version detection or TCP connect scan. When a scan delay is in
               effect, the delay is enforced between each batch of spoofed probes,
               not between each individual probe. Because decoys are sent as a
               batch all at once, they may temporarily violate congestion control
               limits.
    
               It is worth noting that using too many decoys may slow your scan
               and potentially even make it less accurate. Also, some ISPs will
               filter out your spoofed packets, but many do not restrict spoofed
               IP packets at all.
    
           -S IP_Address (Spoof source address) .
               In some circumstances, Nmap may not be able to determine your
               source address (Nmap will tell you if this is the case). In this
               situation, use -S with the IP address of the interface you wish to
               send packets through.
    
               Another possible use of this flag is to spoof the scan to make the
               targets think that someone else is scanning them. Imagine a company
               being repeatedly port scanned by a competitor! The -e option and
               applications stopped working. In particular, DNS may be broken
               because the UDP DNS replies from external servers can no longer
               enter the network. FTP is another common example. In active FTP
               transfers, the remote server tries to establish a connection back
               to the client to transfer the requested file.
    
               Secure solutions to these problems exist, often in the form of
               application-level proxies or protocol-parsing firewall modules.
               Unfortunately there are also easier, insecure solutions. Noting
               that DNS replies come from port 53 and active FTP from port 20,
               many administrators have fallen into the trap of simply allowing
               incoming traffic from those ports. They often assume that no
               attacker would notice and exploit such firewall holes. In other
               cases, administrators consider this a short-term stop-gap measure
               until they can implement a more secure solution. Then they forget
               the security upgrade.
    
               Overworked network administrators are not the only ones to fall
               into this trap. Numerous products have shipped with these insecure
               rules. Even Microsoft has been guilty. The IPsec filters that
               shipped with Windows 2000 and Windows XP contain an implicit rule
               that allows all TCP or UDP traffic from port 88 (Kerberos). In
               another well-known case, versions of the Zone Alarm personal
               firewall up to 2.1.25 allowed any incoming UDP packets with the
               source port 53 (DNS) or 67 (DHCP).
    
               Nmap offers the -g and --source-port options (they are equivalent)
               to exploit these weaknesses. Simply provide a port number and Nmap
               will send packets from that port where possible. Nmap must use
               different port numbers for certain OS detection tests to work
               properly, and DNS requests ignore the --source-port flag because
               Nmap relies on system libraries to handle those. Most TCP scans,
               including SYN scan, support the option completely, as does UDP
               scan.
    
           --data-length number (Append random data to sent packets) .
               Normally Nmap sends minimalist packets containing only a header. So
               its TCP packets are generally 40 bytes and ICMP echo requests are
               just 28. Some UDP ports.  and IP protocols.  get a custom payload
               by default. This option tells Nmap to append the given number of
               random bytes to most of the packets it sends, and not to use any
               protocol-specific payloads. (Use --data-length 0 for no random or
               protocol-specific payloads..  OS detection (-O) packets are not
               affected.  because accuracy there requires probe consistency, but
               most pinging and portscan packets support this. It slows things
               down a little, but can make a scan slightly less conspicuous.
    
           --ip-options S|R [route]|L [route]|T|U ... ; --ip-options hex string
           (Send packets with specified ip options) .
               The IP protocol[13] offers several options which may be placed in
               packet headers. Unlike the ubiquitous TCP options, IP options are
               rarely seen due to practicality and security concerns. In fact,
               string containing 36 NUL bytes.
    
               Nmap also offers a shortcut mechanism for specifying options.
               Simply pass the letter R, T, or U to request record-route,.
               record-timestamp,.  or both options together, respectively. Loose
               or strict source routing.  may be specified with an L or S followed
               by a space and then a space-separated list of IP addresses.
    
               If you wish to see the options in packets sent and received,
               specify --packet-trace. For more information and examples of using
               IP options with Nmap, see
               http://seclists.org/nmap-dev/2006/q3/0052.html.
    
           --ttl value (Set IP time-to-live field) .
               Sets the IPv4 time-to-live field in sent packets to the given
               value.
    
           --randomize-hosts (Randomize target host order) .
               Tells Nmap to shuffle each group of up to 16384 hosts before it
               scans them. This can make the scans less obvious to various network
               monitoring systems, especially when you combine it with slow timing
               options. If you want to randomize over larger group sizes, increase
               PING_GROUP_SZ.  in nmap.h.  and recompile. An alternative solution
               is to generate the target IP list with a list scan (-sL -n -oN
               filename), randomize it with a Perl script, then provide the whole
               list to Nmap with -iL..
    
           --spoof-mac MAC address, prefix, or vendor name (Spoof MAC address) .
               Asks Nmap to use the given MAC address for all of the raw ethernet
               frames it sends. This option implies --send-eth.  to ensure that
               Nmap actually sends ethernet-level packets. The MAC given can take
               several formats. If it is simply the number 0, Nmap chooses a
               completely random MAC address for the session. If the given string
               is an even number of hex digits (with the pairs optionally
               separated by a colon), Nmap will use those as the MAC. If fewer
               than 12 hex digits are provided, Nmap fills in the remainder of the
               six bytes with random values. If the argument isn?t a zero or hex
               string, Nmap looks through nmap-mac-prefixes to find a vendor name
               containing the given string (it is case insensitive). If a match is
               found, Nmap uses the vendor?s OUI (three-byte prefix).  and fills
               out the remaining three bytes randomly. Valid --spoof-mac argument
               examples are Apple, 0, 01:02:03:04:05:06, deadbeefcafe, 0020F2, and
               Cisco. This option only affects raw packet scans such as SYN scan
               or OS detection, not connection-oriented features such as version
               detection or the Nmap Scripting Engine.
    
           --badsum (Send packets with bogus TCP/UDP checksums) .
               Asks Nmap to use an invalid TCP, UDP or SCTP checksum for packets
               sent to target hosts. Since virtually all host IP stacks properly
               drop these packets, any responses received are likely coming from a
               firewall or IDS that didn?t bother to verify the checksum. For more
               details on this technique, see http://nmap.org/p60-12.html
    
           organized and comprehensible fashion. Given the number of ways Nmap is
           used by people and other software, no single format can please
           everyone. So Nmap offers several formats, including the interactive
           mode for humans to read directly and XML for easy parsing by software.
    
           In addition to offering different output formats, Nmap provides options
           for controlling the verbosity of output as well as debugging messages.
           Output types may be sent to standard output or to named files, which
           Nmap can append to or clobber. Output files may also be used to resume
           aborted scans.
    
           Nmap makes output available in five different formats. The default is
           called interactive output,.  and it is sent to standard output
           (stdout)..  There is also normal output,.  which is similar to
           interactive except that it displays less runtime information and
           warnings since it is expected to be analyzed after the scan completes
           rather than interactively.
    
           XML output.  is one of the most important output types, as it can be
           converted to HTML, easily parsed by programs such as Nmap graphical
           user interfaces, or imported into databases.
    
           The two remaining output types are the simple grepable output.  which
           includes most information for a target host on a single line, and
           sCRiPt KiDDi3 0utPUt.  for users who consider themselves |<-r4d.
    
           While interactive output is the default and has no associated
           command-line options, the other four format options use the same
           syntax. They take one argument, which is the filename that results
           should be stored in. Multiple formats may be specified, but each format
           may only be specified once. For example, you may wish to save normal
           output for your own review while saving XML of the same scan for
           programmatic analysis. You might do this with the options -oX
           myscan.xml -oN myscan.nmap. While this chapter uses the simple names
           like myscan.xml for brevity, more descriptive names are generally
           recommended. The names chosen are a matter of personal preference,
           though I use long ones that incorporate the scan date and a word or two
           describing the scan, placed in a directory named after the company I?m
           scanning.
    
           While these options save results to files, Nmap still prints
           interactive output to stdout as usual. For example, the command nmap
           -oX myscan.xml target prints XML to myscan.xml and fills standard
           output with the same interactive results it would have printed if -oX
           wasn?t specified at all. You can change this by passing a hyphen
           character as the argument to one of the format types. This causes Nmap
           to deactivate interactive output, and instead print results in the
           format you specified to the standard output stream. So the command nmap
           -oX - target will send only XML output to stdout..  Serious errors may
           still be printed to the normal error stream, stderr..
    
           Unlike some Nmap arguments, the space between the logfile option flag
           described below.
    
           Nmap Output Formats
    
           -oN filespec (normal output) .
               Requests that normal output be directed to the given filename. As
               discussed above, this differs slightly from interactive output.
    
           -oX filespec (XML output) .
               Requests that XML output be directed to the given filename. Nmap
               includes a document type definition (DTD) which allows XML parsers
               to validate Nmap XML output. While it is primarily intended for
               programmatic use, it can also help humans interpret Nmap XML
               output. The DTD defines the legal elements of the format, and often
               enumerates the attributes and values they can take on. The latest
               version is always available from http://nmap.org/data/nmap.dtd.
    
               XML offers a stable format that is easily parsed by software. Free
               XML parsers are available for all major computer languages,
               including C/C++, Perl, Python, and Java. People have even written
               bindings for most of these languages to handle Nmap output and
               execution specifically. Examples are Nmap::Scanner[15] and
               Nmap::Parser[16] in Perl CPAN. In almost all cases that a
               non-trivial application interfaces with Nmap, XML is the preferred
               format.
    
               The XML output references an XSL stylesheet which can be used to
               format the results as HTML. The easiest way to use this is simply
               to load the XML output in a web browser such as Firefox or IE. By
               default, this will only work on the machine you ran Nmap on (or a
               similarly configured one) due to the hard-coded nmap.xsl filesystem
               path. Use the --webxml or --stylesheet options to create portable
               XML files that render as HTML on any web-connected machine.
    
           -oS filespec (ScRipT KIdd|3 oUTpuT) .
               Script kiddie output is like interactive output, except that it is
               post-processed to better suit the l33t HaXXorZ who previously
               looked down on Nmap due to its consistent capitalization and
               spelling. Humor impaired people should note that this option is
               making fun of the script kiddies before flaming me for supposedly
               "helping them".
    
           -oG filespec (grepable output) .
               This output format is covered last because it is deprecated. The
               XML output format is far more powerful, and is nearly as convenient
               for experienced users. XML is a standard for which dozens of
               excellent parsers are available, while grepable output is my own
               simple hack. XML is extensible to support new Nmap features as they
               are released, while I often must omit those features from grepable
               output for lack of a place to put them.
    
               Nevertheless, grepable output is still quite popular. It is a
               The most important of these fields is generally Ports, which gives
               details on each interesting port. It is a comma separated list of
               port entries. Each port entry represents one interesting port, and
               takes the form of seven slash (/) separated subfields. Those
               subfields are: Port number, State, Protocol, Owner, Service, SunRPC
               info, and Version info.
    
               As with XML output, this man page does not allow for documenting
               the entire format. A more detailed look at the Nmap grepable output
               format is available from
               http://nmap.org/book/output-formats-grepable-output.html.
    
           -oA basename (Output to all formats) .
               As a convenience, you may specify -oA basename to store scan
               results in normal, XML, and grepable formats at once. They are
               stored in basename.nmap, basename.xml, and basename.gnmap,
               respectively. As with most programs, you can prefix the filenames
               with a directory path, such as ~/nmaplogs/foocorp/ on Unix or
               c:\hacking\sco on Windows.
    
           Verbosity and debugging options
    
           -v (Increase verbosity level) .
               Increases the verbosity level, causing Nmap to print more
               information about the scan in progress. Open ports are shown as
               they are found and completion time estimates are provided when Nmap
               thinks a scan will take more than a few minutes. Use it twice or
               more for even greater verbosity.
    
               Most changes only affect interactive output, and some also affect
               normal and script kiddie output. The other output types are meant
               to be processed by machines, so Nmap can give substantial detail by
               default in those formats without fatiguing a human user. However,
               there are a few changes in other modes where output size can be
               reduced substantially by omitting some detail. For example, a
               comment line in the grepable output that provides a list of all
               ports scanned is only printed in verbose mode because it can be
               quite long.
    
           -d [level] (Increase or set debugging level) .
               When even verbose mode doesn?t provide sufficient data for you,
               debugging is available to flood you with much more! As with the
               verbosity option (-v), debugging is enabled with a command-line
               flag (-d) and the debug level can be increased by specifying it
               multiple times..  Alternatively, you can set a debug level by
               giving an argument to -d. For example, -d9 sets level nine. That is
               the highest effective level and will produce thousands of lines
               unless you run a very simple scan with very few ports and targets.
    
               Debugging output is useful when a bug is suspected in Nmap, or if
               you are simply confused as to what Nmap is doing and why. As this
               feature is mostly intended for developers, debug lines aren?t
               or ping. The SYN scan and SYN ping (-sS and -PS) are very detailed,
               but the TCP connect scan (-sT) is limited by the implementation of
               the connect system call. This feature is automatically enabled by
               the debug option (-d).  and the results are stored in XML log files
               even if this option is not specified.
    
           --stats-every time (Print periodic timing stats) .
               Periodically prints a timing status message after each interval of
               time. The time is a specification of the kind described in the
               section called "TIMING AND PERFORMANCE"; so for example, use
               --stats-every 10s to get a status update every 10 seconds. Updates
               are printed to interactive output (the screen) and XML output.
    
           --packet-trace (Trace packets and data sent and received) .
               Causes Nmap to print a summary of every packet sent or received.
               This is often used for debugging, but is also a valuable way for
               new users to understand exactly what Nmap is doing under the
               covers. To avoid printing thousands of lines, you may want to
               specify a limited number of ports to scan, such as -p20-30. If you
               only care about the goings on of the version detection subsystem,
               use --version-trace instead. If you only care about script tracing,
               specify --script-trace. With --packet-trace, you get all of the
               above.
    
           --open (Show only open (or possibly open) ports) .
               Sometimes you only care about ports you can actually connect to
               (open ones), and don?t want results cluttered with closed,
               filtered, and closed|filtered ports. Output customization is
               normally done after the scan using tools such as grep, awk, and
               Perl, but this feature was added due to overwhelming requests.
               Specify --open to only see open, open|filtered, and unfiltered
               ports. These three ports are treated just as they normally are,
               which means that open|filtered and unfiltered may be condensed into
               counts if there are an overwhelming number of them.
    
           --iflist (List interfaces and routes) .
               Prints the interface list and system routes as detected by Nmap.
               This is useful for debugging routing problems or device
               mischaracterization (such as Nmap treating a PPP connection as
               ethernet).
    
           --log-errors (Log errors/warnings to normal mode output file) .
               Warnings and errors printed by Nmap usually go only to the screen
               (interactive output), leaving any normal-format output files
               (usually specified with -oN) uncluttered. When you do want to see
               those messages in the normal output file you specified, add this
               option. It is useful when you aren?t watching the interactive
               output or when you want to record errors while debugging a problem.
               The error and warning messages will still appear in interactive
               mode too. This won?t work for most errors related to bad
               command-line arguments because Nmap may not have initialized its
               output files yet. In addition, some Nmap error and warning messages
               doesn?t work well for XML (-oX) scan data as the resultant file
               generally won?t parse properly until you fix it up by hand.
    
           --resume filename (Resume aborted scan) .
               Some extensive Nmap runs take a very long time--on the order of
               days. Such scans don?t always run to completion. Restrictions may
               prevent Nmap from being run during working hours, the network could
               go down, the machine Nmap is running on might suffer a planned or
               unplanned reboot, or Nmap itself could crash. The administrator
               running Nmap could cancel it for any other reason as well, by
               pressing ctrl-C. Restarting the whole scan from the beginning may
               be undesirable. Fortunately, if normal (-oN) or grepable (-oG) logs
               were kept, the user can ask Nmap to resume scanning with the target
               it was working on when execution ceased. Simply specify the
               --resume option and pass the normal/grepable output file as its
               argument. No other arguments are permitted, as Nmap parses the
               output file to use the same ones specified previously. Simply call
               Nmap as nmap --resume logfilename. Nmap will append new results to
               the data files specified in the previous execution. Resumption does
               not support the XML output format because combining the two runs
               into one valid XML file would be difficult.
    
           --stylesheet path or URL (Set XSL stylesheet to transform XML output) .
               Nmap ships with an XSL stylesheet named nmap.xsl for viewing or
               translating XML output to HTML.  The XML output includes an
               xml-stylesheet directive which points to nmap.xml where it was
               initially installed by Nmap (or in the current working directory on
               Windows). Simply load Nmap?s XML output in a modern web browser and
               it should retrieve nmap.xsl from the filesystem and use it to
               render results. If you wish to use a different stylesheet, specify
               it as the argument to --stylesheet. You must pass the full pathname
               or URL. One common invocation is --stylesheet
               http://nmap.org/data/nmap.xsl. This tells a browser to load the
               latest version of the stylesheet from Nmap.Org. The --webxml option
               does the same thing with less typing and memorization. Loading the
               XSL from Nmap.Org makes it easier to view results on a machine that
               doesn?t have Nmap (and thus nmap.xsl) installed. So the URL is
               often more useful, but the local filesystem location of nmap.xsl is
               used by default for privacy reasons.
    
           --webxml (Load stylesheet from Nmap.Org) .
               This convenience option is simply an alias for --stylesheet
               http://nmap.org/data/nmap.xsl.
    
           --no-stylesheet (Omit XSL stylesheet declaration from XML) .
               Specify this option to prevent Nmap from associating any XSL
               stylesheet with its XML output. The xml-stylesheet directive is
               omitted.
    
    
    

    MISCELLANEOUS OPTIONS

           This section describes some important (and not-so-important) options
           that don?t really fit anywhere else.
               significant use in some (usually Asian) countries and most modern
               operating systems support it. To use Nmap with IPv6, both the
               source and target of your scan must be configured for IPv6. If your
               ISP (like most of them) does not allocate IPv6 addresses to you,
               free tunnel brokers are widely available and work fine with Nmap. I
               use the free IPv6 tunnel broker.  service at
               http://www.tunnelbroker.net. Other tunnel brokers are listed at
               Wikipedia[17]. 6to4 tunnels are another popular, free approach.
    
           -A (Aggressive scan options) .
               This option enables additional advanced and aggressive options. I
               haven?t decided exactly which it stands for yet. Presently this
               enables OS detection (-O), version scanning (-sV), script scanning
               (-sC) and traceroute (--traceroute).  More features may be added in
               the future. The point is to enable a comprehensive set of scan
               options without people having to remember a large set of flags.
               However, because script scanning with the default set is considered
               intrusive, you should not use -A against target networks without
               permission. This option only enables features, and not timing
               options (such as -T4) or verbosity options (-v) that you might want
               as well.
    
           --datadir directoryname (Specify custom Nmap data file location) .
               Nmap obtains some special data at runtime in files named
               nmap-service-probes, nmap-services, nmap-protocols, nmap-rpc,
               nmap-mac-prefixes, and nmap-os-db. If the location of any of these
               files has been specified (using the --servicedb or --versiondb
               options), that location is used for that file. After that, Nmap
               searches these files in the directory specified with the --datadir
               option (if any). Any files not found there, are searched for in the
               directory specified by the NMAPDIR environmental variable.
               ~/.nmap.  for real and effective UIDs (POSIX systems only) or
               location of the Nmap executable (Win32 only), and then a
               compiled-in location such as /usr/local/share/nmap or
               /usr/share/nmap . As a last resort, Nmap will look in the current
               directory.
    
           --servicedb services file (Specify custom services file) .
               Asks Nmap to use the specified services file rather than the
               nmap-services data file that comes with Nmap. Using this option
               also causes a fast scan (-F) to be used. See the description for
               --datadir for more information on Nmap?s data files.
    
           --versiondb service probes file (Specify custom service probes file) .
               Asks Nmap to use the specified service probes file rather than the
               nmap-service-probes data file that comes with Nmap. See the
               description for --datadir for more information on Nmap?s data
               files.
    
           --send-eth (Use raw ethernet sending) .
               Asks Nmap to send packets at the raw ethernet (data link) layer
               rather than the higher IP (network) layer. By default, Nmap chooses
               raw socket sends, packet sniffing, and similar operations that
               usually require root privileges.  on Unix systems. By default Nmap
               quits if such operations are requested but geteuid is not zero.
               --privileged is useful with Linux kernel capabilities and similar
               systems that may be configured to allow unprivileged users to
               perform raw-packet scans. Be sure to provide this option flag
               before any flags for options that require privileges (SYN scan, OS
               detection, etc.). The NMAP_PRIVILEGED.  environmental variable may
               be set as an equivalent alternative to --privileged.
    
           --unprivileged (Assume that the user lacks raw socket privileges) .
               This option is the opposite of --privileged. It tells Nmap to treat
               the user as lacking network raw socket and sniffing privileges.
               This is useful for testing, debugging, or when the raw network
               functionality of your operating system is somehow broken. The
               NMAP_UNPRIVILEGED.  environmental variable may be set as an
               equivalent alternative to --unprivileged.
    
           --release-memory (Release memory before quitting) .
               This option is only useful for memory-leak debugging. It causes
               Nmap to release allocated memory just before it quits so that
               actual memory leaks are easier to spot. Normally Nmap skips this as
               the OS does this anyway upon process termination.
    
           --interactive (Start in interactive mode) .
               Starts Nmap in interactive mode, which offers an interactive Nmap
               prompt allowing easy launching of multiple scans (either
               synchronously or in the background). This is useful for people who
               scan from multi-user systems as they often want to test their
               security without letting everyone else on the system know exactly
               which systems they are scanning. Use --interactive to activate this
               mode and then type h for help. This option is rarely used because
               proper shells are usually more familiar and feature-complete. This
               option includes a bang (!) operator for executing shell commands,
               which is one of many reasons not to install Nmap setuid root..
    
           -V; --version (Print version number) .
               Prints the Nmap version number and exits.
    
           -h; --help (Print help summary page) .
               Prints a short help screen with the most common command flags.
               Running Nmap without any arguments does the same thing.
    
    
    

    RUNTIME INTERACTION

           During the execution of Nmap, all key presses are captured. This allows
           you to interact with the program without aborting and restarting it.
           Certain special keys will change options, while any other keys will
           print out a status message telling you about the scan. The convention
           is that lowercase letters increase the amount of printing, and
           uppercase letters decrease the printing. You may also press '?' for
           help.
    
    
               Stats: 0:00:08 elapsed; 111 hosts completed (5 up), 5 undergoing
               Service Scan
    
               Service scan Timing: About 28.00% done; ETC: 16:18 (0:00:15
               remaining)
    
    
    

    EXAMPLES

           Here are some Nmap usage examples, from the simple and routine to a
           little more complex and esoteric. Some actual IP addresses and domain
           names are used to make things more concrete. In their place you should
           substitute addresses/names from your own network.. While I don?t think
           port scanning other networks is or should be illegal, some network
           administrators don?t appreciate unsolicited scanning of their networks
           and may complain. Getting permission first is the best approach.
    
           For testing purposes, you have permission to scan the host
           scanme.nmap.org. This permission only includes scanning via Nmap and
           not testing exploits or denial of service attacks. To conserve
           bandwidth, please do not initiate more than a dozen scans against that
           host per day. If this free scanning target service is abused, it will
           be taken down and Nmap will report Failed to resolve given hostname/IP:
           scanme.nmap.org. These permissions also apply to the hosts
           scanme2.nmap.org, scanme3.nmap.org, and so on, though those hosts do
           not currently exist.
    
           nmap -v scanme.nmap.org
    
           This option scans all reserved TCP ports on the machine scanme.nmap.org
           . The -v option enables verbose mode.
    
           nmap -sS -O scanme.nmap.org/24
    
           Launches a stealth SYN scan against each machine that is up out of the
           256 IPs on "class C" sized network where Scanme resides. It also tries
           to determine what operating system is running on each host that is up
           and running. This requires root privileges because of the SYN scan and
           OS detection.
    
           nmap -sV -p 22,53,110,143,4564 198.116.0-255.1-127
    
           Launches host enumeration and a TCP scan at the first half of each of
           the 255 possible eight-bit subnets in the 198.116 class B address
           space. This tests whether the systems run SSH, DNS, POP3, or IMAP on
           their standard ports, or anything on port 4564. For any of these ports
           found open, version detection is used to determine what application is
           running.
    
           nmap -v -iR 100000 -PN -p 80
    
           Asks Nmap to choose 100,000 hosts at random and scan them for web
           servers (port 80). Host enumeration is disabled with -PN since first
           Topics include subverting firewalls and intrusion detection systems,
           optimizing Nmap performance, and automating common networking tasks
           with the Nmap Scripting Engine. Hints and instructions are provided for
           common Nmap tasks such as taking network inventory, penetration
           testing, detecting rogue wireless access points, and quashing network
           worm outbreaks. Examples and diagrams show actual communication on the
           wire. More than half of the book is available free online. See
           http://nmap.org/book for more information.
    
    
    

    BUGS

           Like its author, Nmap isn?t perfect. But you can help make it better by
           sending bug reports or even writing patches. If Nmap doesn?t behave the
           way you expect, first upgrade to the latest version available from
           http://nmap.org. If the problem persists, do some research to determine
           whether it has already been discovered and addressed. Try searching for
           the error message on our search page at http://insecure.org/search.html
           or at Google. Also try browsing the nmap-dev archives at
           http://seclists.org/..  Read this full manual page as well. If nothing
           comes of this, mail a bug report to nmap-dev@insecure.org. Please
           include everything you have learned about the problem, as well as what
           version of Nmap you are running and what operating system version it is
           running on. Problem reports and Nmap usage questions sent to
           nmap-dev@insecure.org are far more likely to be answered than those
           sent to Fyodor directly. If you subscribe to the nmap-dev list before
           posting, your message will bypass moderation and get through more
           quickly. Subscribe at
           http://cgi.insecure.org/mailman/listinfo/nmap-dev.
    
           Code patches to fix bugs are even better than bug reports. Basic
           instructions for creating patch files with your changes are available
           at http://nmap.org/data/HACKING. Patches may be sent to nmap-dev
           (recommended) or to Fyodor directly.
    
    
    

    AUTHOR

           Gordon "Fyodor" Lyon fyodor@insecure.org (http://insecure.org)
    
           Hundreds of people have made valuable contributions to Nmap over the
           years. These are detailed in the CHANGELOG.  file which is distributed
           with Nmap and also available from http://nmap.org/changelog.html.
    
    
    

    LEGAL NOTICES

       Nmap Copyright and Licensing
           The Nmap Security Scanner is (C) 1996-2009 Insecure.Com LLC. Nmap is
           also a registered trademark of Insecure.Com LLC. This program is free
           software; you may redistribute and/or modify it under the terms of the
           GNU General Public License as published by the Free Software
           Foundation; Version 2 with the clarifications and exceptions described
           below. This guarantees your right to use, modify, and redistribute this
           software under certain conditions. If you wish to embed Nmap technology
           into proprietary software, we sell alternative licenses (contact
           sales@insecure.com). Dozens of software vendors already license Nmap
           technology such as host discovery, port scanning, OS detection, and
               or execution-menu apps, which simply display raw Nmap output and so
               are not derivative works.)
    
           ?   Integrates/includes/aggregates Nmap into a proprietary executable
               installer, such as those produced by InstallShield.
    
           ?   Links to a library or executes a program that does any of the
               above.
    
           The term "Nmap" should be taken to also include any portions or derived
           works of Nmap. This list is not exclusive, but is meant to clarify our
           interpretation of derived works with some common examples. Our
           interpretation applies only to Nmap--we don?t speak for other people?s
           GPL works.
    
           If you have any questions about the GPL licensing restrictions on using
           Nmap in non-GPL works, we would be happy to help. As mentioned above,
           we also offer alternative license to integrate Nmap into proprietary
           applications and appliances. These contracts have been sold to many
           security vendors, and generally include a perpetual license as well as
           providing for priority support and updates as well as helping to fund
           the continued development of Nmap technology. Please email
           sales@insecure.com for further information.
    
           As a special exception to the GPL terms, Insecure.Com LLC grants
           permission to link the code of this program with any version of the
           OpenSSL library which is distributed under a license identical to that
           listed in the included COPYING.OpenSSL file, and distribute linked
           combinations including the two..  You must obey the GNU GPL in all
           respects for all of the code used other than OpenSSL. If you modify
           this file, you may extend this exception to your version of the file,
           but you are not obligated to do so.
    
           If you received these files with a written license agreement or
           contract stating terms other than the terms above, then that
           alternative license agreement takes precedence over these comments.
    
       Creative Commons License for this Nmap Guide
           This Nmap Reference Guide is (C) 2005-2009 Insecure.Com LLC. It is
           hereby placed under version 3.0 of the Creative Commons Attribution
           License[18]. This allows you redistribute and modify the work as you
           desire, as long as you credit the original source. Alternatively, you
           may choose to treat this document as falling under the same license as
           Nmap itself (discussed previously).
    
       Source Code Availability and Community Contributions
           Source is provided to this software because we believe users have a
           right to know exactly what a program is going to do before they run it.
           This also allows you to audit the software for security holes (none
           have been found so far).
    
           Source code also allows you to port Nmap to new platforms, fix bugs,
           This program is distributed in the hope that it will be useful, but
           WITHOUT ANY WARRANTY; without even the implied warranty of
           MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
           General Public License v2.0 for more details at
           http://www.gnu.org/licenses/gpl-2.0.html, or in the COPYING file
           included with Nmap.
    
           It should also be noted that Nmap has occasionally been known to crash
           poorly written applications, TCP/IP stacks, and even operating
           systems..  While this is extremely rare, it is important to keep in
           mind.  Nmap should never be run against mission critical systems unless
           you are prepared to suffer downtime. We acknowledge here that Nmap may
           crash your systems or networks and we disclaim all liability for any
           damage or problems Nmap could cause.
    
       Inappropriate Usage
           Because of the slight risk of crashes and because a few black hats like
           to use Nmap for reconnaissance prior to attacking systems, there are
           administrators who become upset and may complain when their system is
           scanned. Thus, it is often advisable to request permission before doing
           even a light scan of a network.
    
           Nmap should never be installed with special privileges (e.g. suid root)
           for security reasons..
    
       Third-Party Software
           This product includes software developed by the Apache Software
           Foundation[19]. A modified version of the Libpcap portable packet
           capture library[20].  is distributed along with Nmap. The Windows
           version of Nmap utilized the Libpcap-derived WinPcap library[21].
           instead. Regular expression support is provided by the PCRE
           library[22],.  which is open-source software, written by Philip Hazel..
           Certain raw networking functions use the Libdnet[23].  networking
           library, which was written by Dug Song..  A modified version is
           distributed with Nmap. Nmap can optionally link with the OpenSSL
           cryptography toolkit[24].  for SSL version detection support. The Nmap
           Scripting Engine uses an embedded version of the Lua programming
           language[25]..  All of the third-party software described in this
           paragraph is freely redistributable under BSD-style software licenses.
    
       United States Export Control.
           Nmap only uses encryption when compiled with the optional OpenSSL
           support and linked with OpenSSL. When compiled without OpenSSL support,
           Insecure.Com LLC believes that Nmap is not subject to U.S.  Export
           Administration Regulations (EAR)[26] export control. As such, there is
           no applicable ECCN (explort control classification number) and
           exportation does not require any special license, permit, or other
           governmental authorization.
    
           When compiled with OpenSSL support or distributed as source code,
           Insecure.Com LLC believes that Nmap falls under U.S. ECCN 5D002[27]
           ("Information Security Software"). We distribute Nmap under the TSU
            4. RFC 950
               http://www.rfc-editor.org/rfc/rfc950.txt
    
            5. RFC 1918
               http://www.rfc-editor.org/rfc/rfc1918.txt
    
            6. UDP
               http://www.rfc-editor.org/rfc/rfc768.txt
    
            7. SCTP
               http://www.rfc-editor.org/rfc/rfc4960.txt
    
            8. TCP RFC
               http://www.rfc-editor.org/rfc/rfc793.txt
    
            9. RFC 959
               http://www.rfc-editor.org/rfc/rfc959.txt
    
           10. RFC 1323
               http://www.rfc-editor.org/rfc/rfc1323.txt
    
           11. Lua programming language
               http://lua.org
    
           12. precedence
               http://www.lua.org/manual/5.1/manual.html#2.5.3
    
           13. IP protocol
               http://www.rfc-editor.org/rfc/rfc791.txt
    
           14. RFC 2960
               http://www.rfc-editor.org/rfc/rfc2960.txt
    
           15. Nmap::Scanner
               http://sourceforge.net/projects/nmap-scanner/
    
           16. Nmap::Parser
               http://nmapparser.wordpress.com/
    
           17. listed at Wikipedia
               http://en.wikipedia.org/wiki/List_of_IPv6_tunnel_brokers
    
           18. Creative Commons Attribution License
               http://creativecommons.org/licenses/by/3.0/
    
           19. Apache Software Foundation
               http://www.apache.org
    
           20. Libpcap portable packet capture library
               http://www.tcpdump.org
    
           21. WinPcap library
           26. Export Administration Regulations (EAR)
               http://www.access.gpo.gov/bis/ear/ear_data.html
    
           27. 5D002
               http://www.access.gpo.gov/bis/ear/pdf/ccl5-pt2.pdf
    
           28. EAR 740.13(e)
               http://www.access.gpo.gov/bis/ear/pdf/740.pdf
    
    
    

    Nmap 01/26/2010 NMAP(1)

    
    
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