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 SNORT(8)                                                           SNORT(8)
                                December 2011



 NAME
      Snort - open source network intrusion detection system

 SYNOPSIS
      snort [-bCdDeEfHIMNOpqQsTUvVwWxXy?] [-A alert-mode ] [-B address-
      conversion-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 directory ] [--
      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
      networks.  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 fingerprinting attempts, and much more.  Snort uses a
      flexible rules language 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 alerting 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.




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 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
           verbose 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 running
           Snort as a SHADOW replacement or with a love Of super complex 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
           initialization.  This switch allows Snort to drop root privileges



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           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 verification,
           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 verification
           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) format.
           Ascii logs packets in the old "directories and files" format 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.



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 SNORT(8)                                                           SNORT(8)
                                December 2011



      -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
           obfuscated 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
           information. 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 tcpdump 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.



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      -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 elsewhere,
           use the -c option to specify a valid config-file.

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

      -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 packets.

      -V   Show the version number and exit.

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

      -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.





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      -?   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.




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 SNORT(8)                                                           SNORT(8)
                                December 2011



      --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 directory.




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 SNORT(8)                                                           SNORT(8)
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      --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.



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 SNORT(8)                                                           SNORT(8)
                                December 2011



           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 qualifier, 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 specified 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 contain other
                fields, but you cannot name them explicitly in a filter
                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



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 SNORT(8)                                                           SNORT(8)
                                December 2011



                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 neither
                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
                netmask.  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 destination
                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



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                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 traffic).

           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 protocol
                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 conventions, 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.





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 SNORT(8)                                                           SNORT(8)
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           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 composed of
                integer constants (expressed in standard C syntax), 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



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                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
                (parentheses 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



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                                December 2011



           $ 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.




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 SNORT(8)                                                           SNORT(8)
                                December 2011



           $ 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).




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 SNORT(8)                                                           SNORT(8)
                                December 2011



      SIGUSR1
           Causes the program to dump its current packet statistical
           information 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.snort.org

 AUTHOR
      Martin Roesch <roesch@snort.org>

 SEE ALSO
      tcpdump(1), pcap(3)





















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