Is This Sid Taken? Varonis Hazard Labs | Finds Synthetic Sid Shot Assault

Once a new user or group is created and assigned that specific SID, they automatically inherit all the "synthetic" permissions previously injected, often without appearing in standard audit logs as a new permission grant. Why This Matters

This attack involves threat actors with existing high privileges injecting "synthetic" into an Active Directory Access Control List (ACL) . This allows attackers to pre-assign permissions to a SID that does not yet exist in the environment, creating a silent "backdoor" that activates the moment a new account is created with that matching SID. Key Mechanics of the Attack Once a new user or group is created

A low-level account created later can suddenly "wake up" with Administrative or Domain Admin rights if those rights were pre-injected into the synthetic SID. Key Mechanics of the Attack A low-level account

An attacker with high privileges (but perhaps needing to maintain long-term, hidden access) adds a non-existent SID to a resource's ACL. Once a new user or group is created