Azure AD Connect Health is a feature that allows viewing the health of on-prem hybrid infrastructure components, including Azure AD Connect and AD FS servers. Health information is gathered by agents installed on each on-prem hybrid server. Since March 2021, also AD FS sign-in events are gathered and sent to Azure AD.

In this write-up (based on a Threat Analysis report by Secureworks), I’ll explain how anyone with a local administrator access to AD FS server (or proxy), can create arbitrary sign-ins events to Azure AD sign-ins log. Moreover, I’ll show how Global Administrators can register fake agents to Azure AD - even for tenants not using AD FS at all.

This post is part ⁵⁄₅ of Azure AD and Microsoft 365 kill chain blog series.

Although on-prem administrators doesn’t usually have admin rights to Azure AD, they can have access to crucial information, such as Azure AD Connect, ADFS, and Active Directory. Administrators of these services can easily get admin rights to Azure AD to manipulate and impersonate users.

In this blog, using AADInternals v0.4.0, I’ll show how to get Global Admin access and how to impersonate users as an on-prem administrator.