Passive TCP session reconstruction essential for many kinds of network forensics and law enforcement operations, but it is is complicated by packet loss, retransmissions, and possible attacks by adversaries. The key problem is that participants in the TCP session may observe the TCP segments differently than the monitor. An Added complication is the lack of familiarity with network protocols by many forensic analysts, resulting in the need for tools that are easy-to-use and able to tolerate a wide range of data. To address these issues we rewrote the open source network forensics tool tcpflow, making it more robust to anomalies that had been reported to us by users. We also improved the program’s usability and performance on large packet captures, and added simple visualization that produces a one-page summary PDF for packet captures of any size.

Approved for public release; distribution is unlimited.