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.

• Upgrade to PCRE2
• Add additional level of quiet for certain filtering scenarios
• Update to latest autotools for ngrep and regex-0.12 (2.72, 2023)
• Update manpage for missing options and typos
• Fix BPF DLT_ type detections within libpcap (e.g. DLT_LINUX_SLL)
• Allow for specifying specific location of PCRE2 includes
• Eliminate various non-fatal build warnings (e.g. pcap_lookupdev deprecation)
• Fix ./configure --disable-tcpkill
• Source cleanup (nuke old files, unused vars, missing refs, etc)
• WinXX: -d allows device-name now (e.g. \Device\...)
• WinXX: Removed delay_socket hack in favor of Sleep()
• WinXX: Build with PCRE2 by default
• WinXX: Add new dedicated build script (build.ps1)
• WinXX: Builds on both x86_64 and ARM64 cpu architectures

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.

ngrep was ported extensively to a multitude of platforms, but over time access to them diminished. The list below is the original list; for a current list of confirmed working platforms, see our autobuilds, which includes the most popular OSes, compiler toolchains and cpu architectures.

• 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

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).

• Issues: https://github.com/jpr5/ngrep/issues
• Patches: https://github.com/jpr5/ngrep/pulls

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).

Over the decades (!), ngrep has been included de facto in many popular distributions, several of which have dedicated package maintainers. Many of them have helpfully fielded issues reported by users of their distributions, and have even created patches to ngrep -- but I am seldom made aware. Every few years I have to hunt down what bug reports and patches may exist, in often arcane vendor-specific tracking systems, so that I can incorporate them for everyone's benefit. And sometimes I don't find them all.

If you are a package maintainer for an OS or distribution, and find yourself fielding a bug report or writing a patch for ngrep, please at minimum CC me so that I can track (and possibly solve) the issue. Ideally, send me a link to a patch or pull request so that I can review it and merge it in.

The way I see it, at the end of the day it's my code, so it's my responsibility, but I can't be everywhere to see everything. I need your help to do a good job.

Thank you, sincerely, for all that you have done, and all that you will do. 🙏