The GCP IAM Custom Role Creation detection rule is designed to identify instances of custom role creation within Google Cloud Platform (GCP), which can pose security risks such as privilege escalation. Custom roles are defined by users and allow the combination of permissions to cater to specific operational needs. However, if these roles are created with excessive permissions or by unauthorized users, they can lead to security breaches. This rule monitors audit logs specifically for successful creation events of custom roles, hence offering a layer of visibility into potential misuse. It emphasizes the importance of scrutinizing role creation activities, especially those performed by unfamiliar users or service accounts. The investigation guide provides detailed steps on how to analyze the circumstances surrounding role creations and manage potential false positives effectively. Furthermore, it recommends responding to unauthorized role creations through immediate log review, permission revocation, and policy audits to reinforce the principle of least privilege in access management, thereby enhancing the overall security posture of the environment.