The rule 'O365 Suspicious Rights Delegation' is designed to identify potentially suspicious permissions assigned to users within the Office 365 environment, specifically focusing on the delegation of significant access rights such as FullAccess, SendAs, or SendOnBehalf permissions on user mailboxes. This detection leverages O365 audit logs and the Add-MailboxPermission operation to track instances where one user grants elevated permissions to another. By parsing the parameters of this operation, it filters events based on the specified access rights and aggregates data to highlight the source and destination users, the operation performed, and the specific permissions granted. This monitoring is critical as these high-risk permissions can lead to unauthorized access to sensitive emails, impersonation, or data manipulation, which may suggest insider threats or compromised accounts. Notably, while legitimate use cases exist, the monitoring is vital to detect potential malicious activities, and any detected instances warrant immediate investigation.