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

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

These synthetic entries often appear as "Account Unknown" or long strings of numbers in the security tab, which administrators frequently ignore as remnants of deleted accounts rather than active threats. This attack involves threat actors with existing high

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. A low-level account created later can suddenly "wake

An attacker with high privileges (but perhaps needing to maintain long-term, hidden access) adds a non-existent SID to a resource's ACL. This attack involves threat actors with existing high

Yes, identified a technique known as Synthetic SID Injection .