OSSEC is Free Software, a GPL-licensed, host-based intrusion detection system (HIDS) that operates on a client-server model. Its development is sponsored by Trend Micro, a software security outfit based in Tokyo, Japan.
OSSEC is cross-platform, with binary packages available for all Linux distributions, the BSDs, Windows, Solaris, Mac OS, VMWare ESX, AIX, and HP-UX....
OSSEC Details...