The detection rule "O365 FullAccessAsApp Permission Assigned" tracks the assignment of the high-risk 'full_access_as_app' permission to any application registered in Office 365 Exchange Online. This analytical rule utilizes the Office 365 management activity logs, focusing specifically on Azure Active Directory events to identify instances where this permission, associated with the GUID 'dc890d15-9560-4a4c-9b7f-a736ec74ec40', is granted. The assignment of such permissions is critical as it could potentially allow an application to access sensitive data, send emails impersonating users, or control user mailboxes substantially. The rule triggers an alert when these permissions are reassigned, indicating a risk of unauthorized or malicious activity. It is essential to promptly investigate any alerts generated by this rule to prevent possible data exfiltration or account compromises.