Introduction - If you have any usage issues, please Google them yourself
OSSEC is a scalable, multi-platform, open source Host-based Intrusion Detection System (HIDS). It has a powerful correlation and analysis engine, integrating log analysis, file integrity checking, Windows registry monitoring, centralized policy enforcement, rootkit detection, real-time alerting and active response.
It runs on most operating systems, including Linux, OpenBSD, FreeBSD, MacOS, Solaris and Windows