# Nmap network security scanner man page

    NMAP(1)                                                   NMAP(1)

## NAME

           nmap - Network exploration tool and security scanner

## SYNOPSIS

           nmap [Scan Type(s)] [Options] <host or net #1 ... [#N]>

## DESCRIPTION

           Nmap  is designed to allow system administrators and curi
           ous individuals to scan large networks to determine  which
           hosts  are  up  and what services they are offering.  nmap
           supports a large number of scanning  techniques  such  as:
           UDP, TCP connect(), TCP SYN (half open), ftp proxy (bounce
           attack), Reverse-ident, ICMP (ping sweep), FIN, ACK sweep,
           Xmas Tree, SYN sweep, IP Protocol, and Null scan.  See the
           Scan Types section for more details.  nmap also  offers  a
           number  of  advanced  features such as remote OS detection
           via TCP/IP fingerprinting, stealth scanning, dynamic delay
           and retransmission calculations, parallel scanning, detec
           tion of down hosts via  parallel  pings,  decoy  scanning,
           port  filtering  detection,  direct  (non-portmapper)  RPC
           scanning, fragmentation scanning, and flexible target  and
           port specification.

           Significant  effort  has been put into decent nmap perfor
           mance for non-root users.   Unfortunately,  many  critical
           kernel interfaces (such as raw sockets) require root priv
           ileges.  nmap should be run as root whenever possible (not
           setuid root, of course).

           The  result of running nmap is usually a list of interest
           ing ports on the machine(s) being scanned (if any).   Nmap
           always  gives  the  port's  "well  known" service name (if
           any), number, state, and protocol.  The  state  is  either
           'open',  ´filtered´, or ´unfiltered´.  Open means that the
           target machine will accept()  connections  on  that  port.
           Filtered  means  that a firewall, filter, or other network
           obstacle is covering the port  and  preventing  nmap  from
           determining  whether  the  port is open.  Unfiltered means
           that the port is known by nmap to be closed and  no  fire
           wall/filter  seems  to be interfering with nmap's attempts
           to determine this.  Unfiltered ports are the  common  case
           and  are  only shown when most of the scanned ports are in
           the filtered state.

           Depending on options used, nmap may also report  the  fol
           lowing  characteristics of the remote host: OS in use, TCP
           sequencability, usernames running the programs which  have
           bound  to  each  port, the DNS name, whether the host is a
           smurf address, and a few others.

## OPTIONS

           Options that make sense together  can  generally  be  com
           bined.   Some  options are specific to certain scan modes.
           nmap tries to catch and warn the user about  psychotic  or
           unsupported option combinations.

           If you are impatient, you can skip to the examples section
           at the end, which demonstrates common usage.  You can also
           run  nmap  -h  for  a quick reference page listing all the
           options.

           SCAN TYPES

           -sT    TCP connect() scan: This is the most basic form  of
                  TCP scanning. The connect() system call provided by
                  your operating system is used to open a  connection
                  to  every  interesting  port on the machine. If the
                  port is listening, connect() will  succeed,  other
                  wise the port isn't reachable. One strong advantage
                  to this technique is that you don't need  any  spe
                  cial  privileges.  Any  user  on most UNIX boxes is
                  free to use this call.

                  This sort of scan is easily  detectable  as  target
                  host logs will show a bunch of connection and error
                  messages for the services which accept()  the  con
                  nection just to have it immediately shutdown.

           -sS    TCP  SYN  scan: 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  you
                  wait  for  a response. A SYN|ACK indicates the port
                  is listening. A RST is  indicative  of  a  non-lis
                  tener.   If a SYN|ACK is received, a RST is immedi
                  ately sent to tear down  the  connection  (actually
                  our OS kernel does this for us). The primary advan
                  tage to this scanning technique is that fewer sites
                  will  log  it.   Unfortunately you need root privi
                  leges to build these custom SYN packets.

           -sF -sX -sN
                  Stealth FIN, Xmas Tree, or Null scan  modes:  There
                  are  times when even SYN scanning isn't clandestine
                  enough. Some firewalls and packet filters watch for
                  SYNs to restricted ports, and programs like Synlog
                  ger and Courtney  are  available  to  detect  these
                  scans. These advanced scans, on the other hand, may
                  be able to pass through unmolested.

                  The idea is that closed ports are required to reply
                  to  your probe packet with an RST, while open ports
                  must ignore the packets in question (see RFC 793 pp
                  64).   The  FIN  scan  uses  a  bare (surprise) FIN
                  packet as the probe, while the Xmas tree scan turns
                  on  the  FIN,  URG,  and PUSH flags.  The Null scan
                  turns off all flags.  Unfortunately Microsoft (like
                  usual)  decided  to  completely ignore the standard
                  and do things their own way.  Thus this  scan  type
                  will not work against systems running Windows95/NT.
                  On the positive side, this is a good way to distin
                  guish between the two platforms.  If the scan finds
                  open ports, you know the machine is not  a  Windows
                  box.   If  a  -sF,-sX,or  -sN  scan shows all ports
                  closed, yet a SYN  (-sS)  scan  shows  ports  being
                  opened,  you are probably looking at a Windows box.
                  This is less useful now that  nmap  has  proper  OS
                  detection  built  in.   There  are also a few other
                  systems that are broken in the same way Windows is.
                  They  include  Cisco,  BSDI,  HP/UX, MVS, and IRIX.
                  All of the above send resets from  the  open  ports
                  when they should just drop the packet.

           -sP    Ping  scanning:  Sometimes  you  only  want to know
                  which hosts on a network are up.  Nmap can do  this
                  by  sending  ICMP  echo request packets to every IP
                  address on the networks you  specify.   Hosts  that
                  respond  are up.  Unfortunately, some sites such as
                  microsoft.com block  echo  request  packets.   Thus
                  nmap can also send a TCP ack packet to (by default)
                  port 80.  If we get an RST back,  that  machine  is
                  up.   A  third  technique  involves  sending  a SYN
                  packet and waiting for a RST  or  a  SYN/ACK.   For
                  non-root users, a connect() method is used.

                  By  default  (for  root  users), nmap uses both the
                  ICMP and  ACK  techniques  in  parallel.   You  can
                  change the -P option described later.

                  Note  that  pinging  is done by default anyway, and
                  only hosts that respond are scanned.  Only use this
                  option  if you wish to ping sweep without doing any
                  actual port scans.

           -sU    UDP scans: This method is used to  determine  which
                  UDP  (User  Datagram  Protocol,  RFC 768) ports are
                  open on a host.  The technique is to  send  0  byte
                  udp packets to each port on the target machine.  If
                  we receive an ICMP port unreachable  message,  then
                  the  port  is  closed.   Otherwise  we assume it is
                  open.

                  Some people think UDP scanning is pointless. I usu
                  ally  remind  them  of  the  recent Solaris rcpbind
                  hole. Rpcbind can be found  hiding  on  an  undocu
                  mented  UDP  port  somewhere  above  32770.  So  it
                  doesn't matter that 111 is blocked by the firewall.
                  But can you find which of the more than 30,000 high
                  ports it is listening on? With a  UDP  scanner  you
                  can!   There  is also the cDc Back Orifice backdoor
                  program which hides on a configurable UDP  port  on
                  Windows machines.  Not to mention the many commonly
                  vulnerable services that utilize UDP such as  snmp,
                  tftp, NFS, etc.

                  Unfortunately  UDP  scanning is sometimes painfully
                  slow since most hosts implement a suggestion in RFC
                  1812  (section  4.3.2.8) of limiting the ICMP error
                  message rate.  For example, the  Linux  kernel  (in
                  net/ipv4/icmp.h)   limits  destination  unreachable
                  message generation to 80 per 4 seconds, with a  1/4
                  second  penalty  if  that is exceeded.  Solaris has
                  much more strict limits (about 2 messages per  sec
                  ond)  and  thus  takes  even  longer to scan.  nmap
                  detects this rate limiting and slows  down  accord
                  ingly,  rather  than flood the network with useless
                  packets that will be ignored by the target machine.

                  As  is typical, Microsoft ignored the suggestion of
                  the RFC and does not seem to do any  rate  limiting
                  at  all on Win95 and NT machines.  Thus we can scan
                  all 65K ports of a Windows  machine  very  quickly.
                  Woop!

           -sO    IP protocol scans: This method is used to determine
                  which IP protocols are supported on  a  host.   The
                  technique  is  to  send  raw IP packets without any
                  further protocol header to each specified  protocol
                  on  the target machine.  If we receive an ICMP pro
                  tocol unreachable message, then the protocol is not
                  in use.  Otherwise we assume it is open.  Note that
                  some hosts (AIX, HP-UX, Digital UNIX) and firewalls
                  may  not  send protocol unreachable messages.  This
                  causes all of the protocols to appear "open".

                  Because the implemented technique is  very  similar
                  to  UDP  port scanning, ICMP rate limit might apply
                  too. But the IP protocol field has only 8 bits,  so
                  at most 256 protocols can be probed which should be
                  possible in reasonable time anyway.

           -sI <zombie host[:probeport]>
                  Idlescan: This advanced scan method  allows  for  a
                  truly blind TCP port scan of the target (meaning no
                  packets are sent to the target from  your  real  IP
                  address).   Instead,  a  unique side-channel attack
                  exploits predictable "IP fragmentation ID" sequence
                  generation  on the zombie host to glean information
                  about the open ports on the  target.   IDS  systems
                  will  display  the  scan  as coming from the zombie
                  machine you specify (which must be up and meet cer
                  tain  criteria).   I  am  planning  to  put  a more
                  detailed   explanation   up   at   http://www.inse
                  cure.org/nmap/nmap_documentation.html  in  the near
                  future.

                  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 tar
                  get  using  various zombies that you think might be
                  trusted (via router/packet  filter  rules).   Obvi
                  ously this is crucial information when prioritizing
                  attack targets.  Otherwise, you penetration testers
                  might  have  to expend considerable resources "own
                  ing" an intermediate system, only to find out  that
                  its  IP  isn't even trusted by the target host/net
                  work you are ultimately after.

                  You can add a colon followed by a  port  number  if
                  you  wish  to probe a particular port on the zombie
                  host for IPID changes.  Otherwise Nmap will use the
                  port it uses by default for "tcp pings".

           -sA    ACK  scan:  This advanced method is usually used to
                  map out firewall rulesets.  In particular,  it  can
                  help  determine  whether  a firewall is stateful or
                  just a simple packet filter  that  blocks  incoming
                  SYN packets.

                  This  scan  type  sends  an ACK packet (with random
                  looking acknowledgement/sequence  numbers)  to  the
                  ports specified.  If a RST comes back, the ports is
                  classified as "unfiltered".  If nothing comes  back
                  (or  if  an ICMP unreachable is returned), the port
                  is classified as "filtered".  Note that  nmap  usu
                  ally  doesn't  print "unfiltered" ports, so getting
                  no ports shown in the output is usually a sign that
                  all  the  probes  got  through (and returned RSTs).
                  This scan will obviously never show  ports  in  the
                  "open" state.

           -sW    Window  scan: This advanced scan is very similar to
                  the ACK scan, except that it can  sometimes  detect
                  open  ports  as well as filtered/nonfiltered due to
                  an anomaly in the TCP window size reporting by some
                  operating  systems.   Systems  vulnerable  to  this
                  include at least some versions of AIX, Amiga, BeOS,
                  BSDI,  Cray,  Tru64  UNIX,  DG/UX, OpenVMS, Digital
                  UNIX, FreeBSD, HP-UX, OS/2,  IRIX,  MacOS,  NetBSD,
                  OpenBSD,   OpenStep,   QNX,  Rhapsody,  SunOS  4.X,
                  Ultrix, VAX, and  VxWorks.   See  the  nmap-hackers
                  mailing list archive for a full list.

           -sR    RPC  scan.   This  method works in combination with
                  the various port scan methods of  Nmap.   It  takes
                  all  the  TCP/UDP  ports found open and then 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 firewall (or protected  by  TCP  wrappers).
                  Decoys do not currently work with RPC scan, at some
                  point I may add decoy support for UDP RPC scans.

           -sL    List scan.  This method simply generates and prints
                  a  list  of  IPs/Names  without actually pinging or
                  port scanning them.  DNS name  resolution  will  be
                  performed unless you use -n.

           -b <ftp relay host>
                  FTP  bounce attack: An interesting "feature" of the
                  ftp protocol (RFC 959) is support for  "proxy"  ftp
                  connections.  In  other  words, I should be able to
                  connect from evil.com to the  FTP  server  of  tar
                  get.com  and  request  that  the server send a file
                  ANYWHERE on the internet!  Now this may have worked
                  well  in  1985  when  the  RFC  was written. But in
                  today's Internet, we can't  have  people  hijacking
                  ftp servers and requesting that data be spit out to
                  arbitrary points on the internet. As *Hobbit* wrote
                  back  in  1995,  this protocol flaw "can be used to
                  post virtually untraceable mail and news, hammer on
                  servers at various sites, fill up disks, try to hop
                  firewalls, and generally be annoying  and  hard  to
                  track  down at the same time." What we will exploit
                  this for is to (surprise, surprise) scan TCP  ports
                  from  a  "proxy" ftp server. Thus you could connect
                  to an ftp server behind a firewall, and  then  scan
                  ports  that are more likely to be blocked (139 is a
                  good one). If the ftp server  allows  reading  from
                  and  writing to some directory (such as /incoming),
                  you can send arbitrary data to ports  that  you  do
                  find open (nmap doesn't do this for you though).

                  The  argument  passed to the 'b' option is the host
                  you want to use as a proxy, in standard  URL  nota
                  tion.      The     format     is:    username:pass
                  word@server:port.    Everything   but   server   is
                  optional.  To determine what servers are vulnerable
                  to this attack, you can see my  article  in  Phrack
                  51.   And  updated version is available at the nmap
                  URL (http://www.insecure.org/nmap).

           GENERAL OPTIONS
                  None of these are required but some  can  be  quite
                  useful.

           -P0    Do  not  try  and ping hosts at all before scanning
                  them.  This allows the scanning  of  networks  that
                  don't  allow  ICMP  echo  requests  (or  responses)
                  through their firewall.  microsoft.com is an  exam
                  ple  of  such a network, and thus you should always
                  use -P0 or -PT80 when portscanning microsoft.com.

           -PT    Use TCP "ping" to  determine  what  hosts  are  up.
                  Instead  of  sending  ICMP echo request packets and
                  waiting for a response, we spew out TCP ACK packets
                  throughout  the  target  network  (or  to  a single
                  machine) and then wait  for  responses  to  trickle
                  back.  Hosts that are up should respond with a RST.
                  This option preserves the efficiency of only  scan
                  ning  hosts that are up while still allowing you to
                  scan networks/hosts that block ping  packets.   For
                  non  root users, we use connect().  To set the des
                  tination port of the  probe  packets  use  -PT<port
                  number>.   The  default port is 80, since this port
                  is often not filtered out.

           -PS    This option uses SYN (connection  request)  packets
                  instead  of ACK packets for root users.  Hosts that
                  are up should respond with a  RST  (or,  rarely,  a
                  SYN|ACK).   You can set the destination port in the
                  same manner as -PT above.

           -PI    This option uses a true ping  (ICMP  echo  request)
                  packet.   It finds hosts that are up and also looks
                  for subnet-directed  broadcast  addresses  on  your
                  network.   These  are IP addresses which are exter
                  nally reachable and translate  to  a  broadcast  of
                  incomming  IP  packets  to  a  subnet of computers.
                  These should be eliminated if found as  they  allow
                  for  numerous  denial  of service attacks (Smurf is
                  the most common).

           -PP    Uses an ICMP timestamp request (code 13) packet  to
                  find listening hosts.

           -PM    Same  as  -PI and -PP except uses a netmask request
                  (ICMP code 17).

           -PB    This is the default ping type.  It  uses  both  the
                  ACK ( -PT ) and ICMP echo request ( -PI ) sweeps in
                  parallel.  This way you can get firewalls that fil
                  ter  either one (but not both).  The TCP probe des
                  tination port can be set in the same manner as with
                  -PT above.

           -O     This  option  activates  remote host identification
                  via TCP/IP fingerprinting.  In other words, it uses
                  a  bunch  of techniques to detect subtleties in the
                  underlying operating system network  stack  of  the
                  computers  you are scanning.  It uses this informa
                  tion to create a 'fingerprint'  which  it  compares
                  with  its  database  of  known OS fingerprints (the
                  nmap-os-fingerprints file) to decide what  type  of
                  system you are scanning.

                  If Nmap is unable to guess the OS of a machine, and
                  conditions are good (eg at least  one  open  port),
                  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.  Note
                  that if you leave an IP address on  the  form,  the
                  machine  may be scanned when we add the fingerprint
                  (to validate that it works).

                  The -O option also  enables  several  other  tests.
                  One is the "Uptime" measurement, which uses the TCP
                  timestamp option (RFC 1323) to guess when a machine
                  was  last  rebooted.   This  is  only  reported for
                  machines which provide this information.

                  Another test enabled by -O  is  TCP  Sequence  Pre
                  dictability Classification.  This is a measure that
                  describes approximately how hard it is to establish
                  a  forged  TCP  connection against the remote host.
                  This is useful for exploiting source-IP based trust
                  relationships  (rlogin,  firewall  filters, etc) or
                  for hiding the source of  an  attack.   The  actual
                  difficulty  number is based on statistical sampling
                  and may fluctuate.  It is generally better  to  use
                  the  English  classification  such as "worthy chal
                  lenge" or "trivial joke".  This is only reported in
                  normal output with -v.

                  When verbose mode (-v) is on with -O, IPID 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.

           -I     This  turns on TCP reverse ident scanning. As noted
                  by Dave Goldsmith in a 1996 Bugtraq post, the ident
                  protocol  (rfc  1413)  allows for the disclosure of
                  the username that owns any  process  connected  via
                  TCP,  even if that process didn't initiate the con
                  nection. So you can, for example,  connect  to  the
                  http  port  and then use identd to find out whether
                  the server is running as root.  This  can  only  be
                  done  with a full TCP connection to the target port
                  (i.e. the -sT scanning option).  When -I  is  used,
                  the  remote  host's identd is queried for each open
                  port found.  Obviously this won't work if the  host
                  is not running identd.

           -f     This option causes the requested SYN, FIN, XMAS, or
                  NULL scan 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. My favorite sniffer  segmentation  faulted
                  immediately  upon receiving the first 36-byte frag
                  ment. After that comes a 24 byte  one!  While  this
                  method  won't  get  by packet filters and firewalls
                  that  queue  all  IP  fragments  (like   the   CON
                  FIG_IP_ALWAYS_DEFRAG  option  in the Linux kernel),
                  some networks can't afford the performance hit this
                  causes and thus leave it disabled.

                  Note  that I do not yet have this option working on
                  all systems.  It works fine for my Linux,  FreeBSD,
                  and  OpenBSD  boxes  and  some people have reported
                  success with other *NIX variants.

           -v     Verbose mode.  This is a highly recommended  option
                  and  it  gives  out  more information about what is
                  going on.  You can use it twice for greater effect.
                  Use  -d a couple of times if you really want to get
                  crazy with scrolling the screen!

           -h     This handy option display a quick reference  screen
                  of  nmap  usage  options.  As you may have noticed,
                  this man page is not exactly a 'quick reference' :)

           -oN <logfilename>
                  This  logs  the  results  of your scans in a normal
                  human readable form into the file you specify as an
                  argument.

           -oX <logfilename>
                  This  logs  the  results  of your scans in XML form
                  into the file you specify  as  an  argument.   This
                  allows  programs  to  easily  capture and interpret
                  Nmap results.  You can give the argument ´-´ (with
                  out  quotes) to shoot output into stdout (for shell
                  pipelines, etc).  In this case normal  output  will
                  be suppressed.  Watch out for error messages if you
                  use this (they will still go to stderr).  Also note
                  that  ´-v´  may  cause some extra information to be
                  printed.  The Document Type Definition (DTD) defin
                  ing  the  XML  output  structure  is  available  at
                  http://www.insecure.org/nmap/nmap.dtd .

           -oG <logfilename>
                  This logs the results of your scans in  a  grepable
                  form  into  the  file  you  specify as an argument.
                  This simple format provides all the information  on
                  one  line  (so  you  can easily grep for port or OS
                  information and see all the IPs.  This used  to  be
                  the  preferred  mechanism  for programs to interact
                  with Nmap, but now we  recommend  XML  output  (-oX
                  instead).   This  simple  format may not contain as
                  much information as the  other  formats.   You  can
                  give  the  argument  ´-´  (without quotes) to shoot
                  output into stdout (for shell pipelines, etc).   In
                  this  case normal output will be suppressed.  Watch
                  out for error messages if you use this  (they  will
                  still  go  to  stderr).   Also  note that ´-v´ will
                  cause some extra information to be printed.

           -oA <basefilename>
                  This tells Nmap to log in ALL  the  majore  formats
                  (normal,  grepable,  and XML).  You give a base for
                  the  filename,  and  the  output  files   will   be
                  base.nmap, base.gnmap, and base.xml.

           -oS <logfilename>
                  thIs  l0gz  th3  r3suLtS  of YouR ScanZ iN a s|<ipT
                  kiDd|3 f0rM iNto THe fiL3 U sPecfy 4s an  arGuMEnT!
                  U  kAn  gIv3  the  4rgument ´-´ (wItHOUt qUOteZ) to
                  sh00t output iNT0 stDouT!@!!

           --resume <logfilename>
                  A network scan that is cancelled due to  control-C,
                  network  outage,  etc.  can  be  resumed using this
                  option.  The logfilename must be  either  a  normal
                  (-oN)  or  machine  parsable  (-oM)  log  from  the
                  aborted scan.  No other options can be given  (they
                  will  be  the same as the aborted scan).  Nmap will
                  start on the machine after the  last  one  success
                  fully scanned in the log file.

           --append_output
                  Tells  Nmap  to  append  scan results to any output
                  files you have specified  rather  than  overwriting
                  those files.

           -iL <inputfilename>
                  Reads target specifications from the file specified
                  RATHER than from the command line.  The file should
                  contain  a  list  of  host  or  network expressions
                  seperated by spaces,  tabs,  or  newlines.   Use  a
                  hyphen  (-)  as  inputfilename  if you want nmap to
                  read host expressions from stdin (like at  the  end
                  of  a  pipe).  See the section target specification
                  for more information on the  expressions  you  fill
                  the file with.

           -iR    This option tells Nmap to generate its own hosts to
                  scan by simply picking random numbers :).  It  will
                  never end.  This can be useful for statistical sam
                  pling of the Internet to estimate  various  things.
                  If  you  are ever really bored, try nmap -sS -iR -p
                  80 to find some web servers to look at.

           -p <port ranges>
                  This option specifies what ports you want to  spec
                  ify.  For  example '-p 23' will only try port 23 of
                  the target host(s).   ´-p  20-30,139,60000-´  scans
                  ports  between  20  and 30, port 139, and all ports
                  greater than 60000.  The default  is  to  scan  all
                  ports  between  1  and  1024  as  well as any ports
                  listed in the services file which comes with  nmap.
                  For  IP protocol scanning (-sO), this specifies the
                  protocol number you wish to scan for (0-255).

                  When scanning both TCP and UDP ports, you can spec
                  ify  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  &
                  TCP,  you  have to specify -sU and at least one TCP
                  scan type (such as -sS, -sF, or -sT).  If no proto
                  col  qualifier is given, the port numbers are added
                  to all protocol lists.

           -F Fast scan mode.
                  Specifies that you only  wish  to  scan  for  ports
                  listed  in  the services file which comes with nmap
                  (or the protocols file for -sO).  This is obviously
                  much  faster  than  scanning  all  65535 ports on a
                  host.

           -D <decoy1 [,decoy2][,ME],...>
                  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 extremely  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  repre
                  sent  the  position  you want your IP address to be
                  used.  If your put 'ME'  in  the  6th  position  or
                  later,  some  common  port  scan detectors (such as
                  Solar Designer's excellent scanlogd) are  unlikeley
                  to  show  your IP address at all.  If you don't use
                  'ME', nmap will put you in a random position.

                  Note that the hosts you use as decoys should be  up
                  or  you  might  accidently  SYN flood your targets.
                  Also it will be pretty easy to determine which host
                  is  scanning if only one is actually up on the net
                  work.  You might want to use IP  addresses  instead
                  of  names  (so  the decoy networks don't see you in
                  their nameserver logs).

                  Also note that some (stupid) "port scan  detectors"
                  will  firewall/deny  routing  to hosts that attempt
                  port scans.  Thus you might inadvertantly cause the
                  machine  you  scan  to  lose  connectivity with the
                  decoy machines you are using.  This could cause the
                  target  machines  major  problems  if the decoy is,
                  say, its  internet  gateway  or  even  "localhost".
                  Thus  you  might want to be careful of this option.
                  The real moral of the story is  that  detectors  of
                  spoofable port scans should not take action against
                  the machine that seems like  it  is  port  scanning
                  them.  It could just be a decoy!

                  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 ).

                  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, although many (currently most) do
                  not restrict spoofed IP packets at all.

           -S <IP_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  your 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!  This is not a sup
                  ported usage (or the main purpose) of this flag.  I
                  just  think  it  raises  an interesting possibility
                  that people should  be  aware  of  before  they  go
                  accusing  others  of  port scanning them.  -e would
                  generally be required for this sort of usage.

           -e <interface>
                  Tells nmap what interface to send and receive pack
                  ets  on.  Nmap should be able to detect this but it
                  will tell you if it cannot.

           -g <portnumber>
                  Sets the source port number used  in  scans.   Many
                  naive firewall and packet filter installations make
                  an exception in their ruleset to allow DNS (53)  or
                  FTP-DATA (20) packets to come through and establish
                  a connection.  Obviously this  completely  subverts
                  the  security  advantages  of  the  firewall  since
                  intruders can just masquerade  as  FTP  or  DNS  by
                  modifying  their  source port.  Obviously for a UDP
                  scan you should try 53 first and TCP  scans  should
                  try 20 before 53.  Note that this is only a request
                  -- nmap will honor it only if and when it  is  able
                  to.  For example, you can't do TCP ISN sampling all
                  from  one  host:port  to  one  host:port,  so  nmap
                  changes the source port even if you used -g.

                  Be  aware that there is a small performance penalty
                  on some scans for  using  this  option,  because  I
                  sometimes  store  useful  information in the source
                  port number.

           --data_length <number>
                  Normally Nmap sends minimalistic packets that  only
                  contain a header.  So its TCP packets are generally
                  40 bytes and ICMP echo requests are just 28.   This
                  option  tells  Nmap  to  append the given number of
                  zero-filled bytes to most of the packets it  sends.
                  OS  detection  (-O)  packets  are not affected, but
                  most pinging and portscan packets are.  This  slows
                  things  down, but can be slightly less conspicuous.

           -n     Tells Nmap to NEVER do reverse  DNS  resolution  on
                  the  active  IP  addresses  it finds.  Since DNS is
                  often slow, this can help speed things up.

           -R     Tells Nmap to ALWAYS do reverse DNS  resolution  on
                  the  target  IP  addresses.   Normally this is only
                  done when a machine is found to be alive.

           -r     Tells Nmap NOT to  randomize  the  order  in  which
                  ports are scanned.

           --randomize_hosts
                  Tells  Nmap  to  shuffle  each  group of up to 2048
                  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 (see below).

           -M <max sockets>
                  Sets  the  maximum  number  of sockets that will be
                  used in parallel for  a  TCP  connect()  scan  (the
                  default).   This  is useful to slow down the scan a
                  little bit  and  avoid  crashing  remote  machines.
                  Another  approach is to use -sS, which is generally
                  easier for machines to handle.

           TIMING OPTIONS
                  Generally Nmap does a good  job  at  adjusting  for
                  Network  characteristics at runtime and scanning as
                  fast as possible while minimizing that  chances  of
                  hosts/ports  going  undetected.  However, there are
                  same cases where Nmap's default timing  policy  may
                  not  meet  your  objectives.  The following options
                  provide a fine level of control over the scan  tim
                  ing:

           -T <Paranoid|Sneaky|Polite|Normal|Aggressive|Insane>
                  These  are  canned timing policies for conveniently
                  expressing your priorities to Nmap.  Paranoid  mode
                  scans  very  slowly in the hopes of avoiding detec
                  tion by IDS systems.  It serializes all  scans  (no
                  parallel  scanning)  and generally waits at least 5
                  minutes  between  sending   packets.    Sneaky   is
                  similar,  except  it  only waits 15 seconds between
                  sending packets.  Polite is meant to ease  load  on
                  the  network  and  reduce  the  chances of crashing
                  machines.  It serializes the probes  and  waits  at
                  least  0.4  seconds  between  them.   Normal is the
                  default Nmap  behaviour,  which  tries  to  run  as
                  quickly as possible without overloading the network
                  or missing hosts/ports.  Aggressive mode adds  a  5
                  minute  timeout  per  host  and it never waits more
                  than 1.25 seconds for probe responses.   Insane  is
                  only  suitable  for very fast networks or where you
                  don't mind losing some information.  It  times  out
                  hosts  in 75 seconds and only waits 0.3 seconds for
                  individual probes.  It does allow  for  very  quick
                  network  sweeps  though :).  You can also reference
                  these by number (0-5).  For example, ´-T  0´  gives
                  you Paranoid mode and ´-T 5´ is Insane mode.

                  These  canned  timing  modes  should NOT be used in
                  combination with the  lower  level  controls  given
                  below.

           --host_timeout <milliseconds>
                  Specifies  the  amount  of  time Nmap is allowed to
                  spend scanning a single host before  giving  up  on
                  that IP.  The default timing mode has no host time
                  out.

           --max_rtt_timeout <milliseconds>
                  Specifies  the  maximum  amount  of  time  Nmap  is
                  allowed   to  wait  for  a  probe  response  before
                  retransmitting or timing out that particular probe.
                  The default mode sets this to about 9000.

           --min_rtt_timeout <milliseconds>
                  When  the target hosts start to establish a pattern
                  of responding very quickly, Nmap  will  shrink  the
                  amount of time given per probe.  This speeds up the
                  scan,  but  can  lead  to  missed  packets  when  a
                  response takes longer than usual.  With this param
                  eter you can guarantee that Nmap will wait at least
                  the  given  amount  of  time  before giving up on a
                  probe.

           --initial_rtt_timeout <milliseconds>
                  Specifies the initial probe timeout.  This is  gen
                  erally  only  useful  when scanning firwalled hosts
                  with -P0.  Normally Nmap can obtain good RTT  esti
                  mates  from the ping and the first few probes.  The
                  default mode uses 6000.

           --max_parallelism <number>
                  Specifies the  maximum  number  of  scans  Nmap  is
                  allowed  to  perform  in parallel.  Setting this to
                  one means Nmap will never try to scan more  than  1
                  port  at  a  time.   It also effects other parallel
                  scans such as ping sweep, RPC scan, etc.

           --scan_delay <milliseconds>
                  Specifies the minimum amount of time Nmap must wait
                  between  probes.   This  is mostly useful to reduce
                  network load or to slow the scan way down to  sneak
                  under IDS thresholds.

## TARGET SPECIFICATION

           Everything  that  isn't  an option (or option argument) in
           nmap is treated as a target host specification.  The  sim
           plest  case is listing single hostnames or IP addresses on
           the command line.  If you want to  scan  a  subnet  of  IP
           addresses,  you  can  append '/mask' to the hostname or IP
           address.  mask must be between 0 (scan the whole internet)
           and  32 (scan the single host specified).  Use /24 to scan
           a class 'C' address and /16 for a class 'B'.

           Nmap also has a more  powerful  notation  which  lets  you
           specify an IP address using lists/ranges for each element.
           Thus you can scan the whole class 'B' network  192.168.*.*
           by  specifying  '192.168.*.*'  or '192.168.0-255.0-255' or
           even ´192.168.1-50,51-255.1,2,3,4,5-255'.  And  of  course
           you  can  use  the mask notation: '192.168.0.0/16'.  These
           are all equivalent.  If you use asterisks ('*'),  remember
           that  most  shells  require  you  to escape them with back
           slashes or protect them with quotes.

           Another interesting thing to do is slice the Internet  the
           other  way.   Instead of scanning all the hosts in a class
           specifying hosts to scan, see the examples section.

## EXAMPLES

           Here are some examples of using nmap, from simple and nor
           mal  to  a little more complex/esoteric.  Note that actual
           numbers and some actual domain  names  are  used  to  make
           things  more  concrete.  In their place you should substi
           tute addresses/names from your  own  network.   I  do  not
           think  portscanning  other networks is illegal; nor should
           portscans be construed by others as  an  attack.   I  have
           scanned   hundreds  of  thousands  of  machines  and  have
           received only one complaint.  But I am not  a  lawyer  and
           some  (anal)  people  may  be annoyed by nmap probes.  Get
           permission first or use at your own risk.

           nmap -v target.example.com

           This option scans all reserved TCP ports  on  the  machine
           target.example.com .  The -v means turn on verbose mode.

           nmap -sS -O target.example.com/24

           Launches  a  stealth SYN scan against each machine that is
           up out of the 255 machines on class 'C' where target.exam
           ple.com  resides.  It also tries to determine what operat
           ing system is running on each host that is up and running.
           This  requires root privileges because of the SYN scan and
           the OS detection.

           nmap -sX -p 22,53,110,143,4564 198.116.*.1-127

           Sends an Xmas tree scan to the first half of each  of  the
           255  possible  8  bit  subnets  in  the  198.116 class 'B'
           address space.  We are testing  whether  the  systems  run
           sshd,  DNS,  pop3d,  imapd,  or port 4564.  Note that Xmas
           scan doesn't work on Microsoft boxes due  to  their  defi
           cient  TCP  stack.  Same goes with CISCO, IRIX, HP/UX, and
           BSDI boxes.

           nmap -v --randomize_hosts -p 80 '*.*.2.3-5'

           Rather than focus on a specific IP range, it is  sometimes
           interesting  to  slice  up  the entire Internet and scan a
           small sample from each slice.  This command finds all  web
           servers  on  machines  with  IP  addresses ending in .2.3,
           .2.4, or .2.5 find more interesting machines  starting  at
           127.  so  you  might  want to use '127-222' instead of the
           first asterisks because that section has a greater density
           of interesting machines (IMHO).

           host -l company.com | cut '-d ' -f 4 | ./nmap -v -iL -

           Do  a  DNS  zone transfer to find the hosts in company.com
           and then feed the IP addresses to nmap.   The  above  com
           mands  are  for  my GNU/Linux box.  You may need different
           commands/options on other operating systems.

## BUGS

           Bugs?  What bugs?  Send me any that you find.  Patches are
           nice  too  :) Remember to also send in new OS fingerprints
           so we can grow the database.  Nmap will give you a submis
           sion URL when an appropriate fingerprint is found.

## AUTHOR

           Fyodor <fyodor@insecure.org>

## DISTRIBUTION

           The   newest   version   of  nmap  can  be  obtained  from
           http://www.insecure.org/nmap/

           nmap is (C) 1995-2001 by Insecure.Com LLC

           libpcap is also distributed along with nmap.  It is  copy
           righted  by  Van Jacobson, Craig Leres and Steven McCanne,
           all of the Lawrence Berkeley National Laboratory,  Univer
           sity of California, Berkeley, CA.  The version distributed
           with nmap may be modified, pristine sources are  available
           from ftp://ftp.ee.lbl.gov/libpcap.tar.Z .

           This  program  is  free  software; you can redistribute it
           and/or modify it under the terms of the GNU General Public
           License as published by the Free Software Foundation; Ver
           sion 2.  This guarantees your right to  use,  modify,  and
           redistribute  Nmap  under  certain  conditions.   If  this
           license is unacceptable to you, Insecure.Org may be  will
           ing  to  sell  alternative  licenses (contact fyodor@inse
           cure.org).

           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, and add new features.  You are highly encouraged
           to send your changes to fyodor@insecure.org  for  possible
           incorporation  into  the  main  distribution.   By sending
           these changes to Fyodor or one the  insecure.org  develop
           ment  mailing  lists,  it is assumed that you are offering
           Fyodor the unlimited, non-exclusive right to  reuse,  mod
           ify,  and  relicense  the code.  This is important because
           the inability to relicense  code  has  caused  devastating
           problems for other Free Software projects (such as KDE and
           NASM).  Nmap will always be available Open Source.  If you
           wish to specify special license conditions of your contri
           butions, just say so when you send them.

           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 for more
           details (it is in the COPYING file of the  nmap  distribu
           tion).

           It  should also be noted that Nmap has been known to crash
           certain poorly written applications,  TCP/IP  stacks,  and
           even  operating systems.  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.

           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 run with privileges  (eg  suid  root)
           for security reasons.

           All  versions  of  Nmap  equal  to or greater than 2.0 are
           believed to be Year 2000 (Y2K) compliant in all  respects.
           There  is  no  reason to believe versions earlier than 2.0
           are susceptible to problems, but we have not tested  them.

                                                              NMAP(1)