Office 365 Mail Accessed by Unexpected Entra ID Application
Detects when mail items are accessed via API through an Entra ID application that is not explicitly approved. This rule specifically looks for 'MailItemsAccessed' events in Office 365 where the accessing application's ClientAppId does not match known legitimate Microsoft applications like Exchange Online, Substrate Context Service, or Microsoft Office. This could indicate unauthorized access to mailboxes by a suspicious application.
YARA-L
