The purpose of an intrusion detection system (IDS) is to monitor network traffic and identify suspicious activities or potential security breaches. IDS tools analyze data packets and alert administrators to potential intrusions, unauthorized access, or anomalies that could indicate a cyber attack. They can operate as either network-based or host-based systems, with the former focusing on the network level and the latter monitoring individual devices. By providing real-time alerts, IDS helps organizations enhance their security posture and respond proactively to threats.