How Does an Intrusion Detection System (IDS) Work?

Executive summary: This article explains what Intrusion Detection Systems (IDS) are, how they function, and why they remain relevant as part of a layered security strategy. It covers IDS types (network and host), detection approaches (signature, anomaly, hybrid), the typical detection lifecycle (traffic capture, analysis, alerting, integration), deployment and tuning recommendations, common detection capabilities and blind spots (e.g., encrypted traffic, supply-chain risks), and how IDS can be enhanced via SIEM/SOAR integration and managed services to improve detection and triage.