An Intrusion Detection System (IDS) is a network security tool that monitors network traffic for suspicious activity and alerts security personnel or automated systems of potential security incidents. IDS can be network-based (NIDS) or host-based (HIDS), and use various techniques such as signature-based detection, anomaly-based detection, and behavioral analysis to detect potential security incidents. IDS can quickly detect and respond to potential security incidents, reducing the impact of a security breach on an organization's systems and data.