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Entra ID OAuth Flow by Microsoft Authentication Broker to Device Registration Service (DRS)

Identifies separate OAuth authorization flows in Microsoft Entra ID where the same user principal and session ID are observed across multiple IP addresses within a 5-minute window. These flows involve the Microsoft…

Description

Identifies separate OAuth authorization flows in Microsoft Entra ID where the same user principal and session ID are observed across multiple IP addresses within a 5-minute window. These flows involve the Microsoft Authentication Broker (MAB) as the client application and the Device Registration Service (DRS) as the target resource. This pattern is highly indicative of OAuth phishing activity, where an adversary crafts a legitimate Microsoft login URL to trick a user into completing authentication and sharing the resulting authorization code, which is then exchanged for an access and refresh token by the attacker.

Detection logic

Its licence does not clear it for publishing here

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Detection requirements

Platform
ContainersESXiIaaSIdentity ProviderLinuxmacOSNetwork DevicesOffice SuiteSaaSWindows

The rule states no platform. This is derived from the 4 ATT&CK techniques it maps to.

Known benign triggers

  • Legitimate device registrations using Microsoft Authentication Broker may occur during corporate enrollment scenarios or bulk provisioning, but it is uncommon for multiple source IPs to register the same identity across Microsoft Graph, Device Registration Service (DRS), and Azure Active Directory (AAD) in a short time span.

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