Deception Toolkit - - Make your system seem to have network security bugs, and log attack attempts.
FakeBo - - Fakes trojan servers (Back Orifice, NetBus) and logs every attempt from client.
Flawfinder - - Examines source code looking for security weaknesses.
Guarded Memory Move (GMM) - - The GMM library can be used to prevent and study buffer overflows exploit.
Libsafe - - Free software (GNU license) from Bell Labs for protecting internet servers from buffer overflow attacks, one of the most commonly exploited security vulnerabilities.
Samhain - - A tool for file integrity checking that optionally can be used as a client/server application for centralized monitoring of networked hosts.