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Microsoft Graph Email Access by Unusual User and Client

Identifies access to email resources via Microsoft Graph API using an first-party application on behalf of a user principal. This behavior may indicate an adversary using a phished OAuth refresh token or a Primary…

Description

Identifies access to email resources via Microsoft Graph API using an first-party application on behalf of a user principal. This behavior may indicate an adversary using a phished OAuth refresh token or a Primary Refresh Token (PRT) to access email resources. The pattern includes requests to Microsoft Graph API endpoints related to email, such as /me/mailFolders/inbox/messages or /users/{user_id}/messages, using a public client application ID and a user principal object ID. This is a New Terms rule that only signals if the application ID, user principal object ID, and source ASN have not been seen doing this activity historically.

Detection logic

Its licence does not clear it for publishing here

Sunturai publishes a detection's own text where the licence it arrived under has been reviewed and permits it, and Elastic License 2.0 has not. The query as its source wrote it, its canonical form and the hash that pins this revision are in the workspace record.

Detection requirements

Platform
ContainersIaaSIdentity ProviderLinuxmacOSOffice SuiteSaaSWindows

The rule states no platform. This is derived from the 2 ATT&CK techniques it maps to.

Log source category
event_index

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