This rule monitors changes to user group memberships within Google Cloud Platform (GCP) with a focus on adding users to privileged groups that have special access rights. It is designed to detect when a user is added to a group classified as having elevated privileges, which could indicate potential unauthorized access or misconfigured permissions. If a user is added to a group like 'admins@example.com', which is typically reserved for administrative users, it raises a flag for investigation. The rule uses GCP audit logs to identify relevant add group member activities captured via `google.admin.AdminService.addGroupMember` calls. It requires a single event within a defined time period to trigger an alert, prompting a review of the circumstances surrounding the membership change. Given the sensitive nature of group membership changes, the rule operates with a low sensitivity level, indicating it may require further contextual evaluation. An accompanying runbook suggests reviewing the legitimacy of user additions to privileged groups.