OSSEC HIDS 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.
It runs on most operating systems, including Linux, MacOS, Solaris, HP-UX, AIX and Windows.
Check out OSSEC features and how it works for more information about how OSSEC can help you solve your host-based security problems.
Download Here :: ossec-agent-win32-2.7.exe (For Windows)
ossec-hids-2.7.1-beta-1.tar.gz (For Linux/BSD)
Official Website :: http://www.ossec.net/