Microsoft

Microsoft Azure Activity Log (formerly Azure Audit Log) is a platform log that provides visibility into subscription-level events across Azure resources. It records control-plane operations such as resource creation, modification, deletion, role assignments, policy changes, and service health events for all Azure Resource Manager operations. 

The Activity Log is essential for security monitoring in Azure environments, capturing who performed what action, on which resource, and when. It enables detection of unauthorized resource modifications, privilege escalation through role assignments, security policy changes, and suspicious administrative activities, providing the audit trail needed for compliance and incident investigation.