An Intrusion Detection System (IDS) is a security tool that monitors network traffic for suspicious activity or policy violations, alerting administrators when potential threats are detected.

A common use case for IDS is identifying unauthorized access attempts, malware infections, or unusual behavior in a network. IDS monitors traffic by analyzing data packets, using predefined rules (signatures) or behavior patterns (anomalies) to detect threats.

It typically sits on the network at critical points, such as behind a firewall or near key servers, to capture and analyze relevant traffic.

Suricata, a popular open-source IDS, excels in detecting threats by using deep packet inspection and multi-threading to analyze network traffic in real-time efficiently.