OSSEC

OSSEC is an Open Source Host-based Intrusion Detection System that performs log analysis, file integrity checking, policy monitoring, rootkit detection, real-time alerting, and active response.

OSSEC is a scalable, multi-platform, open source Host-based Intrusion Detection System (HIDS). OSSEC has a powerful correlation and analysis engine, integrating log analysis, file integrity monitoring, 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.