OSSEC

OSSEC is a widely deployed, open-source host-based intrusion detection system (HIDS) engineered to deliver comprehensive file integrity monitoring (FIM), centralized log analysis, rootkit detection, and active automated response across Linux, Unix, Windows, and macOS endpoints. Operating via lightweight agent daemons communicating securely with a centralized manager, OSSEC performs continuous security auditing of host operating systems. The engine's file integrity monitoring continuously scans system binaries, configuration files, and registry entries, alerting administrators immediately if file attributes, checksums, or permissions change, which is vital for detecting backdoor installations and malicious tampering. OSSEC analyzes system logs, application logs, and authentication records in real time, matching log events against an extensive rule engine to uncover brute-force SSH logins, unauthorized privilege escalations, and web application attack attempts. When high-severity security incidents occur, OSSEC executes configurable Active Response scripts to automatically block attacking IP addresses via local firewalls or terminate compromised user sessions. Backed by an active global open-source community, OSSEC provides enterprise IT organizations with a robust, cost-effective host security solution that fulfills mandatory FIM requirements for PCI-DSS, HIPAA, and CIS benchmarks.