Upgrade to OSSEC+ for Free
OSSEC+ provides additional capabilities to the basic OSSEC version such as the Machine Learning System for those that simply register. The cost is still free but OSSEC+ does more!
OSSEC is an Open Source Host based Intrusion Detection System. It performs log analysis, integrity checking, Windows registry monitoring, rootkit detection, real-time alerting and active response. It runs on most operating systems, including Linux, OpenBSD, FreeBSD, Mac OS X, Solaris and Windows. A list with all supported platforms is available at: Supported Systems
OSSEC