OSSEC

OSSEC is an open-source host-based intrusion detection system that gives security teams visibility into activity occurring directly on servers and endpoints. Its capabilities include log analysis, file integrity checking, Windows registry monitoring, rootkit detection, real-time alerting and active response. Because it operates at the host level, OSSEC can complement network security tools by identifying changes or suspicious activity that may not be obvious from network traffic alone. The project supports multiple operating systems, including Linux, Windows and several Unix-like platforms, making it adaptable to mixed infrastructure. Security teams can use OSSEC to monitor sensitive files, investigate system events and create alerts around policy violations or unexpected changes. Its open-source architecture also allows organizations to integrate it with broader logging and security operations workflows. OSSEC is particularly relevant to administrators and security teams that need lightweight host monitoring without adopting a proprietary endpoint platform.