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snort(8)                                                              snort(8)




NAME

       Snort - open source network intrusion detection system


SYNOPSIS

       snort  [-bCdDeEfHIMNOpqQsTUvVwWxXy?]  [-A alert-mode ] [-B address-con-
       version-mask ] [-c rules-file ] [-F bpf-file ] [-g group-name ] [-G  id
       ] [-h home-net ] [-i interface ] [-k checksum-mode ] [-K logging-mode ]
       [-l log-dir ] [-L bin-log-file ] [-m umask ]  [-n  packet-count  ]  [-P
       snap-length  ]  [-r  tcpdump-file ] [-R name ] [-S variable=value ] [-t
       chroot_directory ] [-u  user-name  ]  [-Z  pathname  ]  [--logid  id  ]
       [--perfmon-file  pathname  ]  [--pid-path  pathname  ] [--snaplen snap-
       length  ]  [--help  ]  [--version  ]   [--dynamic-engine-lib   file   ]
       [--dynamic-engine-lib-dir  directory  ] [--dynamic-detection-lib file ]
       [--dynamic-detection-lib-dir directory ]  [--dump-dynamic-rules  direc-
       tory  ] [--dynamic-preprocessor-lib file ] [--dynamic-preprocessor-lib-
       dir directory ] [--dynamic-output-lib file ]  [--dynamic-output-lib-dir
       directory  ]  [--alert-before-pass ] [--treat-drop-as-alert ] [--treat-
       drop-as-ignore  ]  [--process-all-events  ]   [--enable-inline-test   ]
       [--create-pidfile   ]  [--nolock-pidfile  ]  [--no-interface-pidfile  ]
       [--disable-attribute-reload-thread  ]  [--pcap-single=  tcpdump-file  ]
       [--pcap-filter=  filter ] [--pcap-list= list ] [--pcap-dir= directory ]
       [--pcap-file= file ] [--pcap-no-filter ] [--pcap-reset ] [--pcap-reload
       ]  [--pcap-show  ] [--exit-check count ] [--conf-error-out ] [--enable-
       mpls-multicast   ]   [--enable-mpls-overlapping-ip    ]    [--max-mpls-
       labelchain-len  ]  [--mpls-payload-type  ] [--require-rule-sid ] [--daq
       type ] [--daq-mode mode ] [--daq-var  name=value  ]  [--daq-dir  dir  ]
       [--daq-list  [dir] ] [--dirty-pig ] [--cs-dir dir ] [--ha-peer ] [--ha-
       out file ] [--ha-in file ] expression


DESCRIPTION

       Snort is an open source network intrusion detection system, capable  of
       performing  real-time  traffic  analysis  and packet logging on IP net-
       works.  It can perform protocol  analysis,  content  searching/matching
       and  can  be  used  to  detect a variety of attacks and probes, such as
       buffer overflows, stealth port scans, CGI attacks, SMB probes, OS  fin-
       gerprinting  attempts, and much more.  Snort uses a flexible rules lan-
       guage to describe traffic that it should collect or pass, as well as  a
       detection  engine  that  utilizes a modular plugin architecture.  Snort
       also has a modular real-time alerting capability, incorporating  alert-
       ing and logging plugins for syslog, a ASCII text files, UNIX sockets or
       XML.

       Snort has three primary uses.  It can be  used  as  a  straight  packet
       sniffer  like  tcpdump(1),  a packet logger (useful for network traffic
       debugging, etc), or as a full blown network intrusion detection system.

       Snort  logs  packets  in tcpdump(1) binary format or in Snort's decoded
       ASCII format to a hierarchy of logging directories that are named based
       on the IP address of the "foreign" host.


OPTIONS

       -A alert-mode
              Alert using the specified alert-mode.  Valid alert modes include
              fast, full, none, and unsock.  Fast writes alerts to the default
              "alert" file in a single-line, syslog style alert message.  Full
              writes the alert to the  "alert"  file  with  the  full  decoded
              header  as  well as the alert message.  None turns off alerting.
              Unsock is an experimental mode that sends the alert  information
              out  over a UNIX socket to another process that attaches to that
              socket.

       -b     Log packets in a tcpdump(1) formatted file.    All  packets  are
              logged  in  their native binary state to a tcpdump formatted log
              file named with the snort start timestamp and "snort.log".  This
              option results in much faster operation of the program
               since  it doesn't have to spend time in the packet binary->text
              converters.  Snort can keep up pretty well with 100Mbps networks
              in  '-b'  mode.   To choose an alternate name for the binary log
              file, use the '-L' switch.

       -B address-conversion-mask
              Convert all IP addresses in home-net to addresses  specified  by
              address-conversion-mask.   Used to obfuscate IP addresses within
              binary logs. Specify home-net with the '-h' switch.   Note  this
              is not the same as $HOME_NET.

       -c config-file
              Use the rules located in file config-file.

       -C     Print  the character data from the packet payload only (no hex).

       -d     Dump the application layer data when displaying packets in  ver-
              bose or packet logging mode.

       -D     Run    Snort    in    daemon   mode.    Alerts   are   sent   to
              /var/log/snort/alert unless otherwise specified.

       -e     Display/log the link layer packet headers.

       -E     *WIN32 ONLY* Log alerts to the Windows Event Log.

       -f     Activate PCAP line buffering

       -F bpf-file
              Read BPF filters from bpf-file.  This is handy for  people  run-
              ning  Snort as a SHADOW replacement or with a love Of super com-
              plex BPF filters.  See the "expressions"  section  of  this  man
              page for more info on writing BPF filters.

       -g group
              Change the group/GID Snort runs under to group after initializa-
              tion.  This switch allows Snort to drop  root  privileges  after
              it's initialization phase has completed as a security measure.

       -G id  Use id as a base event ID when logging events.

       -h home-net
              Set  the "home network" to home-net.  The format of this address
              variable is  a  network  prefix  plus  a  CIDR  block,  such  as
              192.168.1.0/24.   Once  this variable is set, all decoded packet
              logging will be done relative to the home network address space.
              This  is  useful because of the way that Snort formats its ASCII
              log data.  With this value set to the local network, all decoded
              output  will  be logged into decode directories with the address
              of the foreign computer as the directory  name,  which  is  very
              useful  during  traffic  analysis.  This  option does not change
              "$HOME_NET" in IDS mode.

       -H     Force hash tables to be deterministic instead of using a  random
              number  generator  for the seed & scale.  Useful for testing and
              generating repeatable results with the same traffic.

       -i interface
              Sniff packets on interface.

       -I     Print out the receiving interface name in alerts.

       -k checksum-mode
              Tune  the  internal  checksum  verification  functionality  with
              alert-mode.   Valid  checksum  modes  include  all, noip, notcp,
              noudp, noicmp, and none.  All  activates  checksum  verification
              for all supported protocols.  Noip turns off IP checksum verifi-
              cation, which is handy if the gateway router is already dropping
              packets that fail their IP checksum checks.  Notcp turns off TCP
              checksum verification, all other checksum modes are  on.   noudp
              turns  off  UDP  checksum  verification.   Noicmp turns off ICMP
              checksum verification.  None turns off the entire checksum veri-
              fication subsystem.

       -K logging-mode
              Select  a  packet  logging mode.  The default is pcap.  logging-
              mode.  Valid logging modes include pcap, ascii, and none.   Pcap
              logs  packets  through the pcap library into pcap (tcpdump) for-
              mat.  Ascii logs packets in the old "directories and files" for-
              mat  with  packet printouts in each file.  None Turns off packet
              logging.

       -l log-dir
              Set the output logging directory to  log-dir.   All  plain  text
              alerts  and  packet logs go into this directory.  If this option
              is not specified,  the  default  logging  directory  is  set  to
              /var/log/snort.

       -L binary-log-file
              Set  the filename of the binary log file to binary-log-file.  If
              this switch is not used, the default name is a timestamp for the
              time that the file is created plus "snort.log".

       -m umask
              Set the file mode creation mask to umask

       -M     Log  console  messages  to  syslog when not running daemon mode.
              Using both -D and -M will send all messages to syslog  including
              e.g.  SIGUSR1  dump  packet  stats. This switch has no impact on
              logging of alerts.

       -n packet-count
              Process packet-count packets and exit.

       -N     Turn off packet logging.  The  program  still  generates  alerts
              normally.

       -O     Obfuscate the IP addresses when in ASCII packet dump mode.  This
              switch  changes  the  IP  addresses  that  get  printed  to  the
              screen/log  file  to  "xxx.xxx.xxx.xxx".  If the homenet address
              switch is set (-h), only addresses on the homenet will be obfus-
              cated  while non- homenet IPs will be left visible.  Perfect for
              posting to your favorite security mailing list!

       -p     Turn off promiscuous mode sniffing.

       -P snap-length
              Set the packet snaplen to snap-length.  By default, this is  set
              to 1514.

       -q     Quiet  operation. Don't display banner and initialization infor-
              mation. In daemon mode, banner and initialization information is
              not logged to syslog.

       -Q     Enable inline mode operation.

       -r tcpdump-file
              Read  the  tcpdump-formatted file tcpdump-file.  This will cause
              Snort to read and process the file fed to it.   This  is  useful
              if,  for  instance,  you've got a bunch of SHADOW files that you
              want to process for content, or even if you've got  a  bunch  of
              reassembled packet fragments which have been written into a tcp-
              dump formatted file.

       -R name
              Use name as a suffix to the snort pidfile.

       -s     Send alert messages to syslog.  On linux boxen, they will appear
              in /var/log/secure, /var/log/messages on many other platforms.

       -S variable=value
              Set  variable  name "variable" to value "value".  This is useful
              for setting the value of a defined  variable  name  in  a  Snort
              rules  file to a command line specified value.  For instance, if
              you define a HOME_NET variable name  inside  of  a  Snort  rules
              file,  you  can set this value from it's predefined value at the
              command line.

       -t chroot
              Changes Snort's root directory to chroot  after  initialization.
              Please  note  that  all  log/alert filenames are relative to the
              chroot directory if chroot is used.

       -T     Snort will start up in self-test mode, checking all the supplied
              command  line switches and rules files that are handed to it and
              indicating that everything is ready to proceed.  This is a  good
              switch  to  use  if daemon mode is going to be used, it verifies
              that the Snort configuration that is about to be used  is  valid
              and  won't  fail  at  run  time.  Note,  Snort  looks for either
              /etc/snort.conf or ./snort.conf.  If  your  config  lives  else-
              where, use the -c option to specify a valid config-file.

       -u user
              Change  the  user/UID Snort runs under to user after initializa-
              tion.

       -U     Changes the timestamp in all logs to be in UTC

       -v     Be verbose.  Prints packets out to the console.   There  is  one
              big  problem with verbose mode: it's slow.  If you are doing IDS
              work with Snort, don't use the '-v' switch, you WILL drop  pack-
              ets.

       -V     Show the version number and exit.

       -w     Show  management  frames if running on an 802.11 (wireless) net-
              work.

       -W     *WIN32 ONLY* Enumerate the network interfaces available.

       -x     Exit if Snort configuration problems  occur  such  as  duplicate
              gid/sid or flowbits without Stream5.

       -X     Dump  the  raw  packet  data  starting  at the link layer.  This
              switch overrides the '-d' switch.

       -y     Include the year in alert and log files

       -Z pathname
              Set the perfmonitor preprocessor path/filename to pathname.

       -?     Show the program usage statement and exit.

       --logid id
              Same as -G.

       --perfmon-file pathname
              Same as -Z.

       --pid-path directory
              Specify the directory for the Snort PID file.

       --snaplen snap-length
              Same as -P.

       --help Same as -?

       --version
              Same as -V

       --dynamic-engine-lib file
              Load a dynamic detection  engine  shared  library  specified  by
              file.

       --dynamic-engine-lib-dir directory
              Load  all  dynamic  detection  engine shared libraries specified
              from directory.

       --dynamic-detection-lib file
              Load a dynamic detection rules shared library specified by file.

       --dynamic-detection-lib-dir directory
              Load all dynamic detection rules shared libraries specified from
              directory.

       --dump-dynamic-rules directory
              Create stub rule files from all loaded dynamic  detection  rules
              libraries.   Files  will  be  created  in  directory.   This  is
              required to be done prior to running snort using those detection
              rules  and  the  generated  rules  files  must  be  included  in
              snort.conf.

       --dynamic-preprocessor-lib file
              Load a dynamic preprocessor shared library specified by file.

       --dynamic-preprocessor-lib-dir directory
              Load all dynamic preprocessor shared  libraries  specified  from
              directory.

       --alert-before-pass
              Process  alert,  drop, sdrop, or reject before pass.  Default is
              pass before alert, drop, etc.

       --treat-drop-as-alert
              Converts drop, sdrop, and reject rules into alert  rules  during
              startup.

       --treat-drop-as-ignore
              Use drop, sdrop, and reject rules to ignore session traffic when
              not inline.

       --process-all-events
              Process all triggered events in group order, per  Rule  Ordering
              configuration.  Default stops after first group.

       --enable-inline-test
              Enable Inline-Test Mode Operation.

       --pid-path directory
              Specify the path for Snort's PID file.

       --create-pidfile
              Create PID file, even when not in Daemon mode.

       --nolock-pidfile
              Do not try to lock Snort PID file.

       --no-interface-pidfile
              Do not include the interface name in Snort PID file

       --pcap-single=tcpdump-file
              Same as -r.  Added for completeness.

       --pcap-filter=filter
              Shell  style  filter  to  apply  when getting pcaps from file or
              directory.  This filter will apply to any --pcap-file or --pcap-
              dir  arguments following.  Use --pcap-no-filter to delete filter
              for following --pcap-file or  --pcap-dir  arguments  or  specify
              --pcap-filter  again  to  forget previous filter and to apply to
              following --pcap-file or --pcap-dir arguments.

       --pcap-list="list"
              A space separated list of pcaps to read.

       --pcap-dir=directory
              A directory to recurse to  look  for  pcaps.   Sorted  in  ascii
              order.

       --pcap-file=file
              File that contains a list of pcaps to read.  Can specify path to
              pcap or directory to recurse to get pcaps.

       --pcap-no-filter
              Reset to use no filter when getting pcaps from  file  or  direc-
              tory.

       --pcap-reset
              If  reading  multiple  pcaps,  reset snort to post-configuration
              state before reading next pcap.  The default, i.e. without  this
              option, is not to reset state.

       --pcap-show
              Print a line saying what pcap is currently being read.

       --exit-check=count
              Signal  termination  after <count> callbacks from DAQ_Acquire(),
              showing the time it takes from  signaling  until  DAQ_Stop()  is
              called.

       --conf-error-out
              Same as -x.

       --require-rule-sid
              Require  an  SID  for  every  rule to be correctly threshold all
              rules.

       --daq <type>
              Select packet acquisition module (default is pcap).

       --daq-mode <mode>
              Select the DAQ operating mode.

       --daq-var <name=value>
              Specify extra DAQ configuration variable.

       --daq-dir <dir>
              Tell Snort where to find desired DAQ.

       --daq-list [<dir>]
              List packet acquisition modules available in dir.

       --cs-dir <dir>
              Tell Snort to use control socket and create the socket in dir.


        expression
              selects which packets will  be  dumped.   If  no  expression  is
              given,  all  packets on the net will be dumped.  Otherwise, only
              packets for which expression is `true' will be dumped.

              The expression consists of one or more  primitives.   Primitives
              usually  consist  of  an  id (name or number) preceded by one or
              more qualifiers.  There are three different kinds of qualifier:

              type   qualifiers say what kind of thing the id name  or  number
                     refers to.  Possible types are host, net and port.  E.g.,
                     `host foo', `net 128.3', `port 20'.  If there is no  type
                     qualifier, host is assumed.

              dir    qualifiers  specify  a  particular  transfer direction to
                     and/or from id.  Possible directions are src, dst, src or
                     dst  and  src and dst.  E.g., `src foo', `dst net 128.3',
                     `src or dst port ftp-data'.  If there is  no  dir  quali-
                     fier,  src  or  dst  is  assumed.  For `null' link layers
                     (i.e. point to point protocols such as slip) the  inbound
                     and  outbound qualifiers can be used to specify a desired
                     direction.

              proto  qualifiers restrict the match to a  particular  protocol.
                     Possible  protos are: ether, fddi, ip, arp, rarp, decnet,
                     lat, sca, moprc, mopdl, tcp and udp.   E.g.,  `ether  src
                     foo',  `arp  net  128.3',  `tcp port 21'.  If there is no
                     proto qualifier, all protocols consistent with  the  type
                     are  assumed.  E.g., `src foo' means `(ip or arp or rarp)
                     src foo' (except the latter is not  legal  syntax),  `net
                     bar'  means  `(ip  or arp or rarp) net bar' and `port 53'
                     means `(tcp or udp) port 53'.

              [`fddi' is actually an alias for `ether'; the parser treats them
              identically  as meaning ``the data link level used on the speci-
              fied network interface.''  FDDI  headers  contain  Ethernet-like
              source  and  destination  addresses, and often contain Ethernet-
              like packet types, so you can filter on these FDDI  fields  just
              as  with  the analogous Ethernet fields.  FDDI headers also con-
              tain other fields, but you cannot name them explicitly in a fil-
              ter expression.]

              In  addition  to  the  above, there are some special `primitive'
              keywords that don't  follow  the  pattern:  gateway,  broadcast,
              less,  greater  and  arithmetic  expressions.   All of these are
              described below.

              More complex filter expressions are built up by using the  words
              and,  or and not to combine primitives.  E.g., `host foo and not
              port ftp and not port  ftp-data'.   To  save  typing,  identical
              qualifier lists can be omitted.  E.g., `tcp dst port ftp or ftp-
              data or domain' is exactly the same as `tcp dst port ftp or  tcp
              dst port ftp-data or tcp dst port domain'.

              Allowable primitives are:

              dst host host
                     True  if  the IP destination field of the packet is host,
                     which may be either an address or a name.

              src host host
                     True if the IP source field of the packet is host.

              host host
                     True if either the IP source or destination of the packet
                     is  host.   Any  of  the  above  host  expressions can be
                     prepended with the keywords, ip, arp, or rarp as in:
                          ip host host
                     which is equivalent to:
                          ether proto \ip and host host
                     If host is  a  name  with  multiple  IP  addresses,  each
                     address will be checked for a match.

              ether dst ehost
                     True if the ethernet destination address is ehost.  Ehost
                     may be either a name from /etc/ethers or  a  number  (see
                     ethers(3N) for numeric format).

              ether src ehost
                     True if the ethernet source address is ehost.

              ether host ehost
                     True if either the ethernet source or destination address
                     is ehost.

              gateway host
                     True if the packet used host as  a  gateway.   I.e.,  the
                     ethernet  source or destination address was host but nei-
                     ther the IP source nor the IP destination was host.  Host
                     must  be  a name and must be found in both /etc/hosts and
                     /etc/ethers.  (An equivalent expression is
                          ether host ehost and not host host
                     which can be used with either names or numbers for host /
                     ehost.)

              dst net net
                     True  if  the  IP destination address of the packet has a
                     network number of net. Net may  be  either  a  name  from
                     /etc/networks  or  a  network number (see networks(4) for
                     details).

              src net net
                     True if the IP source address of the packet has a network
                     number of net.

              net net
                     True  if  either  the IP source or destination address of
                     the packet has a network number of net.

              net net mask mask
                     True if the IP address matches net with the specific net-
                     mask.  May be qualified with src or dst.

              net net/len
                     True  if  the  IP  address matches net a netmask len bits
                     wide.  May be qualified with src or dst.

              dst port port
                     True if the packet is ip/tcp or ip/udp and has a destina-
                     tion  port  value of port.  The port can be a number or a
                     name used in /etc/services (see tcp(4P) and udp(4P)).  If
                     a  name  is  used,  both the port number and protocol are
                     checked.  If a number or ambiguous name is used, only the
                     port  number  is  checked  (e.g., dst port 513 will print
                     both tcp/login traffic  and  udp/who  traffic,  and  port
                     domain  will  print  both tcp/domain and udp/domain traf-
                     fic).

              src port port
                     True if the packet has a source port value of port.

              port port
                     True if either the source  or  destination  port  of  the
                     packet is port.  Any of the above port expressions can be
                     prepended with the keywords, tcp or udp, as in:
                          tcp src port port
                     which matches only tcp packets whose source port is port.

              less length
                     True  if  the  packet  has a length less than or equal to
                     length.  This is equivalent to:
                          len <= length.

              greater length
                     True if the packet has a length greater than or equal  to
                     length.  This is equivalent to:
                          len >= length.

              ip proto protocol
                     True if the packet is an ip packet (see ip(4P)) of proto-
                     col type protocol.  Protocol can be a number  or  one  of
                     the  names  icmp,  igrp,  udp, nd, or tcp.  Note that the
                     identifiers tcp, udp, and icmp are also keywords and must
                     be escaped via backslash (\), which is \\ in the C-shell.

              ether broadcast
                     True if the packet is an ethernet broadcast packet.   The
                     ether keyword is optional.

              ip broadcast
                     True  if the packet is an IP broadcast packet.  It checks
                     for both the all-zeroes and  all-ones  broadcast  conven-
                     tions, and looks up the local subnet mask.

              ether multicast
                     True  if the packet is an ethernet multicast packet.  The
                     ether  keyword  is  optional.   This  is  shorthand   for
                     `ether[0] & 1 != 0'.

              ip multicast
                     True if the packet is an IP multicast packet.

              ether proto protocol
                     True  if  the packet is of ether type protocol.  Protocol
                     can be a number or a name like ip, arp,  or  rarp.   Note
                     these  identifiers  are also keywords and must be escaped
                     via backslash (\).  [In the case  of  FDDI  (e.g.,  `fddi
                     protocol  arp'),  the  protocol identification comes from
                     the 802.2 Logical Link Control  (LLC)  header,  which  is
                     usually  layered  on  top  of  the  FDDI header.  Tcpdump
                     assumes, when filtering on the protocol identifier,  that
                     all  FDDI packets include an LLC header, and that the LLC
                     header is in so-called SNAP format.]

              decnet src host
                     True if the DECNET source address is host, which  may  be
                     an address of the form ``10.123'', or a DECNET host name.
                     [DECNET host name support is  only  available  on  Ultrix
                     systems that are configured to run DECNET.]

              decnet dst host
                     True if the DECNET destination address is host.

              decnet host host
                     True  if  either the DECNET source or destination address
                     is host.

              ip, arp, rarp, decnet
                     Abbreviations for:
                          ether proto p
                     where p is one of the above protocols.

              lat, moprc, mopdl
                     Abbreviations for:
                          ether proto p
                     where p is one of the above protocols.  Note  that  Snort
                     does not currently know how to parse these protocols.

              tcp, udp, icmp
                     Abbreviations for:
                          ip proto p
                     where p is one of the above protocols.

              expr relop expr
                     True  if  the relation holds, where relop is one of >, <,
                     >=, <=, =, !=, and expr is an arithmetic expression  com-
                     posed  of integer constants (expressed in standard C syn-
                     tax), the normal binary operators [+, -, *, /, &,  |],  a
                     length  operator,  and special packet data accessors.  To
                     access data inside the packet, use the following syntax:
                          proto [ expr : size ]
                     Proto is one of ether, fddi, ip, arp, rarp, tcp, udp,  or
                     icmp,  and  indicates  the  protocol  layer for the index
                     operation.  The byte offset, relative  to  the  indicated
                     protocol  layer,  is given by expr.  Size is optional and
                     indicates the number of bytes in the field  of  interest;
                     it  can be either one, two, or four, and defaults to one.
                     The length operator, indicated by the keyword len,  gives
                     the length of the packet.

                     For  example,  `ether[0]  & 1 != 0' catches all multicast
                     traffic.  The expression `ip[0] & 0xf != 5'  catches  all
                     IP packets with options. The expression `ip[6:2] & 0x1fff
                     = 0' catches only unfragmented datagrams and frag zero of
                     fragmented  datagrams.   This check is implicitly applied
                     to the tcp  and  udp  index  operations.   For  instance,
                     tcp[0] always means the first byte of the TCP header, and
                     never means the first byte of an intervening fragment.

              Primitives may be combined using:

                     A parenthesized group of primitives and operators (paren-
                     theses are special to the Shell and must be escaped).

                     Negation (`!' or `not').

                     Concatenation (`&&' or `and').

                     Alternation (`||' or `or').

              Negation  has highest precedence.  Alternation and concatenation
              have equal precedence and associate left to  right.   Note  that
              explicit  and  tokens,  not  juxtaposition, are now required for
              concatenation.

              If an identifier is given without a  keyword,  the  most  recent
              keyword is assumed.  For example,
                   not host vs and ace
              is short for
                   not host vs and host ace
              which should not be confused with
                   not ( host vs or ace )

              Expression  arguments  can be passed to Snort as either a single
              argument or as multiple arguments, whichever is more convenient.
              Generally,  if  the expression contains Shell metacharacters, it
              is easier to pass it as a  single,  quoted  argument.   Multiple
              arguments are concatenated with spaces before being parsed.


READING PCAPS

       Instead  of  having  Snort  listen  on  an interface, you can give it a
       packet capture to read.  Snort will read and analyze the packets as  if
       they  came  off the wire.  This can be useful for testing and debugging
       Snort.

       Read a single pcap

            $ snort -r foo.pcap
            $ snort --pcap-single=foo.pcap

       Read pcaps from a file

            $ cat foo.txt
            foo1.pcap
            foo2.pcap
            /home/foo/pcaps

            $ snort --pcap-file=foo.txt

            This  will  read  foo1.pcap,  foo2.pcap  and   all   files   under
            /home/foo/pcaps.   Note  that  Snort  will  not  try  to determine
            whether the files under that directory are really  pcap  files  or
            not.

       Read pcaps from a command line list

            $ snort --pcap-list="foo1.pcap foo2.pcap foo3.pcap"

            This will read foo1.pcap, foo2.pcap and foo3.pcap.

       Read pcaps under a directory

            $ snort --pcap-dir="/home/foo/pcaps"

            This will include all of the files under /home/foo/pcaps.

       Using filters

            $ cat foo.txt
            foo1.pcap
            foo2.pcap
            /home/foo/pcaps

            $ snort --pcap-filter="*.pcap" --pcap-file=foo.txt
            $ snort --pcap-filter="*.pcap" --pcap-dir=/home/foo/pcaps

            The  above  will  only  include files that match the shell pattern
            "*.pcap", in other words, any file ending in ".pcap".

            $ snort --pcap-filter="*.pcap --pcap-file=foo.txt \
            > --pcap-filter="*.cap" --pcap-dir=/home/foo/pcaps

            In the above, the first filter "*.pcap" will only  be  applied  to
            the  pcaps  in  the  file  "foo.txt" (and any directories that are
            recursed in that file).  The addition of the second filter "*.cap"
            will  cause  the  first filter to be forgotten and then applied to
            the directory /home/foo/pcaps, so only files ending in ".cap" will
            be included from that directory.

            $ snort --pcap-filter="*.pcap --pcap-file=foo.txt \
            > --pcap-no-filter --pcap-dir=/home/foo/pcaps

            In this example, the first filter will be applied to foo.txt, then
            no  filter  will   be   applied   to   the   files   found   under
            /home/foo/pcaps,  so all files found under /home/foo/pcaps will be
            included.

            $ snort --pcap-filter="*.pcap --pcap-file=foo.txt \
            > --pcap-no-filter --pcap-dir=/home/foo/pcaps \
            > --pcap-filter="*.cap" --pcap-dir=/home/foo/pcaps2

            In this example, the first filter will be applied to foo.txt, then
            no   filter   will   be   applied   to   the   files  found  under
            /home/foo/pcaps, so all files found under /home/foo/pcaps will  be
            included,  then  the filter "*.cap" will be applied to files found
            under /home/foo/pcaps2.

       Resetting state

            $ snort --pcap-dir=/home/foo/pcaps --pcap-reset

            The  above  example   will   read   all   of   the   files   under
            /home/foo/pcaps,  but after each pcap is read, Snort will be reset
            to  a  post-configuration  state,  meaning  all  buffers  will  be
            flushed,  statistics  reset,  etc.  For each pcap, it will be like
            Snort is seeing traffic for the first time.

       Printing the pcap

            $ snort --pcap-dir=/home/foo/pcaps --pcap-show

            The above example will read all of the files under /home/foo/pcaps
            and  will  print  a  line indicating which pcap is currently being
            read.


RULES

       Snort uses a simple but flexible rules  language  to  describe  network
       packet  signatures  and associate them with actions.  The current rules
       document can be found at http://www.snort.org/snort-rules.


NOTES

       The following signals have the specified effect when sent to the daemon
       process using the kill(1) command:


       SIGHUP Causes the daemon to close all opened files and restart.  Please
              note that this will only work if the full pathname  is  used  to
              invoke snort in daemon mode, otherwise snort will just exit with
              an error message being sent to syslogd(8).


       SIGUSR1
              Causes the program to dump its current packet statistical infor-
              mation to the console or syslogd(8) if in daemon mode.


       SIGUSR2
              Causes the program to rotate Perfmonitor statistical information
              to the console or syslogd(8) if in daemon mode.


       SIGURG Causes the program to reload attribute table.


       SIGCHLD
              Used internally.

       Please refer to manual for more details. Any other signal  might  cause
       the daemon to close all opened files and exit.



HISTORY

       Snort has been freely available under the GPL license since 1998.


DIAGNOSTICS

       Snort returns a 0 on a successful exit, 1 if it exits on an error.


BUGS

       After  consulting  the BUGS file included with the source distribution,
       send bug reports to snort-devel@lists.sourceforge.net


AUTHOR

       Martin Roesch <roesch@snort.org>


SEE ALSO

       tcpdump(1), pcap(3)



                                 December 2011                        snort(8)

snort 2.9.12 - Generated Tue Feb 19 14:37:41 CST 2019
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