The Internet is awash in intrusion opportunities. One unpatched exploit can let an intruder slip through the perimeter defenses. As a result, computers owned by unsuspecting citizens and businesses can mutate into spam slingers, distributing malicious programs or spying on users. How do you know if an intruder is on your computer? The host-based intrusion detection system Tripwire quietly monitors the filesystem and promptly notifies you in case of any changes.

Numerous IDS systems exist for the free Linux operating system, both for whole networks (Network-based Intrusion Detection System, NIDS) and for individual hosts (Host-based Intrusion Detection System, HIDS). The first category includes Snort, Suricata, and Prelude, which ideally detect attacks on entire networks. The second category includes applications such PortSentry, Logcheck, Samhain, OSSEC, and, last but not least, Tripwire [1].

Tripwire is a file integrity checker. The system was developed in 1992 by Gene Kim and Dr. Eugene Spafford at Purdue University [2]. Since 1999, Tripwire Inc. [3] has further developed the application as Tripwire Enterprise.

[...]