ngrep

ngrep is like GNU grep applied to the network layer. It's a PCAP-based tool that allows you to specify an extended regular or hexadecimal expression to match against data payloads of packets. It understands many kinds of protocols, including IPv4/6, TCP, UDP, ICMPv4/6, IGMP and Raw, across a wide variety of interface types, and understands BPF filter logic in the same fashion as more common packet sniffing tools, such as tcpdump and snoop.

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ngrep 1.47 (9.7.2017)

ngrep is like GNU grep applied to the network layer. It’s a PCAP-based tool
that allows you to specify an extended regular or hexadecimal expression to
match against data payloads of packets. It understands many kinds of protocols,
including IPv4/6, TCP, UDP, ICMPv4/6, IGMP and Raw, across a wide variety of
interface types, and understands BPF filter logic in the same fashion as more
common packet sniffing tools, such as tcpdump and snoop.

What’s New

  • Fix “no VLAN support for XXX”-related problems
  • Fix truncated/garbled output (e.g. SIP over SLL/Linux cooked sockets)
  • Change exit behavior to match BSD & GNU grep (see manpage)
  • Add Solaris IPnet support
  • Update to use 32bit values where relevant
  • Emit frame # in header, useful for reference/analysis
  • Emit total received, matched upon exit (dropped unreliable PCAP stats)
  • Import debian patches related to autotools, manpage, and compilation on other platforms
  • Fix build clean/distclean when not linked against provided GNU regex
  • Fix build --enable/–disable flag processing
  • Fix building under MS VS2012 / Win32
  • Update to latest autotools (2017)

How to use

ngrep was originally developed to:

  • debug plaintext protocol interactions such as HTTP, IMAP, DNS, SIP, etc.
  • identify and analyze anomalous network communications such as those between
    malware, zombies and viruses
  • store, read and reprocess pcap dump files while looking for specific data
    patterns

As well, it could be used to do plaintext credential collection, as with HTTP
Basic Authentication, FTP or POP3 authentication. Like all useful tools, it can
be used for good and for bad.

Visit EXAMPLES to learn more about how ngrep works and can be
leveraged to see all sorts of neat things.

Support, Feedback, & Patches

If you need help, have constructive feedback, or would like to submit a patch,
please visit ngrep’s project at GitHub and use the online tools there. It will
help the author better manage the various requests and patches so that nothing
is lost or missed (as has been the case in the past, unfortunately).

Confirmed Working Platforms

  • Linux 2.0+ (RH6+, SuSE, TurboLinux, Debian, Gentoo, Ubuntu, Mandrake, Slackware)/x86, RedHat/alpha Cobalt, (Qube2) Linux/MIPS
  • Solaris 2.5.1, 2.6/SPARC, Solaris 7, Solaris 8/SPARC, Solaris 9/SPARC
  • FreeBSD 2.2.5, 3.1, 3.2, 3.4-RC, 3.4-RELEASE, 4.0, 5.0
  • OpenBSD 2.4 (after upgrading pcap from 0.2), 2.9, 3.0, 3.1+
  • NetBSD 1.5/SPARC
  • Digital Unix V4.0D (OSF/1), Tru64 5.0, Tru64 5.1A
  • HPUX 11
  • IRIX
  • AIX 4.3.3.0/PowerPC
  • BeOS R5
  • Mac OS X 10+
  • GNU HURD
  • Windows 95, 98, NT, 2000, XP, 2003/x86, 7, 8, 8.1, 10

Miscellany

Please see CREDITS for a partial list of the many people who helped make ngrep
what it is today. Also, please note that ngrep is released under a simple
BSD-style license, though depending on which regex library you compile
against, you’ll either get the GPL (GNU regex) or Artistic (PCRE).