A security information and event management (SIEM) system collects logs and security events from sources such as endpoints, servers, identity services, and network devices. It normalizes and correlates this data, helping security teams detect suspicious patterns, investigate incidents, and monitor activity from a central place.
SIEM rules and alerts depend on reliable telemetry and correctly parsed logs. In real attacks, correlation can reveal activity that looks harmless in isolation, such as a sequence of unusual logins followed by access to sensitive systems. In defense, teams test and tune SIEM rules and check that changes to log formats or collection pipelines have not stopped expected alerts from firing. A SIEM supports detection and analysis; it does not guarantee that every threat will be identified.