Microsoft synchronization capabilities for managing identities in hybrid environments are not without their risks. In this blog, Tenable Research explores how potential weaknesses in these synchronization options can be exploited.

Synchronizing identity accounts between Microsoft Active Directory (AD) and Entra ID is important for user experience, as it seamlessly synchronizes user identities, credentials and groups between on-premises and cloud-based systems. At the same time, Tenable Research shows the following synchronization options can introduce cybersecurity risk that extend beyond hybrid tenants:

the already known Directory Synchronization Accounts Entra role
the new On Premises Directory Sync Account Entra role
the new Microsoft Entra AD Synchronization Service application
In 2024, Microsoft introduced two new security hardening measures for hybrid Entra ID synchronization. However, despite these improvements, both the Directory Synchronization Accounts and the new On Premises Directory Sync Account roles retain access to critical synchronization APIs. Moreover, the new 'Microsoft Entra AD Synchronization Service' application exposes the privileged ADSynchronization.ReadWrite.All permission, introducing another potential attack path that security teams must watch closely.

In this technical blog, we break down the changes Microsoft made to each of its synchronization options, explore where new risks were introduced and provide guidance on how Tenable Identity Exposure can help you monitor and secure your hybrid synchronization environment.