tcpxtract is a tool for extracting files from network traffic based on file signatures. Extracting files based on file type headers and footers (sometimes called “carving”) is an age old data recovery technique. Tools like Foremost employ this technique to recover files from arbitrary data streams. tcpxtract uses this technique specifically for the application of intercepting files transmitted across a network.

Other tools that fill a similar need are driftnet and EtherPEG. driftnet and EtherPEG are tools for monitoring and extracting graphic files on a network and is commonly used by network administrators to police the internet activity of their users. The major limitations of driftnet and EtherPEG is that they only support three filetypes with no easy way of adding more. The search technique they use is also not scalable and does not search across packet boundries.

tcpxtract features the following:

• Supports 26 popular file formats out-of-the-box. New formats can be added by simply editing its config file.
• With a quick conversion, you can use your old Foremost config file with tcpxtract.
• Custom written search algorithm is lightning fast and very scalable.
• Search algorithm searches across packet boundries for total coverage and forensic quality.
• Uses libpcap, a popular, portable and stable library for network data capture.
• Can be used against a live network or a tcpdump formatted capture file.

You can download tcpxtract here:

tcpxtract Version 1.0.1 source

Or read more here.