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.

Microsoft changed the location of ADSync encryption keys in Azure AD Connect version 1.4.x. These keys are used to encrypt and decrypt the passwords of “service accounts” used for syncing data from AD to Azure AD. Earlier versions saved the keys in the registry, but currently, it is using DPAPI. Thus, AADInternals couldn’t decrypt the passwords anymore. Luckily, Dirk-jan Mollema described in his great article how the encryption keys could be extracted and used to decrypt the passwords. Using Dirk-jan’s article as a starting point, I decided to implement this to AADInternals.