Security Information and Event Management - software that collects and analyzes security data from across an organization to detect threats. Like having a security command center that monitors all cameras and sensors.
Security teams use SIEM to correlate login failures, network anomalies, and suspicious file access into a single view for threat detection.
SIEM is a capability rather than a single product. Microsoft Sentinel and Google Security Operations are cloud-native SIEM/SOAR platforms. AWS commonly implements SIEM using Amazon Security Lake (centralized security data lake) plus analytics/detection tools (often partner SIEMs). OCI Logging Analytics can centralize and analyze logs and is often used as a core component in SIEM-style monitoring, typically complemented by additional detection/response tooling.