Bit-Twist is a simple yet powerful libpcap-based Ethernet packet generator. It is designed to complement tcpdump, which by itself has done a great job at capturing network traffic.

With Bit-Twist, you can now regenerate your captured traffic onto a live network! Packets are generated from tcpdump trace file (.pcap file). Bit-Twist also comes with a comprehensive trace file editor to allow you to change the contents of a trace file.

Generally, packet generator is useful in simulating networking traffic or scenario, testing firewall, IDS, and IPS, and troubleshooting various network problems.


These are just a few significant features that makes Bit-Twist unique and stands out as one of the best Ethernet packet generator package made available to the open source community.

  • Runs on Mac OS X (and *BSD), Linux, and Windows
  • Send multiple trace files at a time
  • Send packets at a specific speed or line rate in Mbps
  • Comprehensive trace file editor with control over most fields in Ethernet, ARP, IP, ICMP, TCP, and UDP headers with automatic header checksum correction
  • Append user payload to existing packets after a specific header
  • Select a specific range of packets and save them in another trace file
  • Highly scriptable - with proper manipulation you can turn Bit-Twist into an extremely flexible packet generator tool!


Latest development version is Bit-Twist 2.0, released on April 21, 2012.

Mac OS X bittwist-macosx-2.0.tar.gz (MD5 = e6e36e267ed111b0f9a311dedc691c67) Linux bittwist-linux-2.0.tar.gz (MD5 = 8a93e0ae5df3172dabf154ccfd31c49f) Windows (pre-compiled binary files included, Cygwin DLL is required) (MD5 = 038a9994ec8248649904d9736509a108) IMPORTANT: If you do not have Cygwin environment installed, download and unzip into any directory visible to your path, e.g. C:/WINDOWS/system32

You may download Bit-Twist from File Releases for Bit-Twist. Older releases are available here for regression testing.


Please do not hesitate to file and send your bug report directly to me at Make sure you are using the latest version before submitting your bug report. Known bugs are described in Bit-Twist manual pages under the BUGS section.


Bit-Twist project is maintained and developed by Addy Yeow Chin Heng.