The 'GCP Service Account Access Denied' rule is designed to detect and alert on access denial events related to Google Cloud Platform (GCP) service accounts, specifically when there are attempts made to create service accounts without proper permissions. The rule utilizes GCP audit logs as its primary data source, monitoring for events where a service account creation request fails due to insufficient permissions. The rule includes a threshold configuration, such that if at least 30 such events occur within a 5-minute period, an alert will be triggered. This filtering helps reduce false positives caused by transient access issues or legitimate permission denials. The provided runbook advises users to verify the expected nature of these denial events, as they may indicate an adversary's attempts to manipulate service account permissions in order to gain unauthorized access or perform malicious actions, emphasizing the importance of maintaining proper access controls and auditing.