Fast Facts

• Researchers uncovered a new attack path exploiting Active Directory Sites for privilege escalation.
• Misconfigured access controls (ACLs) on AD Sites allow attackers to move between domains undetected.
• Most organizations focus security on users and domain controllers, ignoring the hidden risks of site infrastructure.
• Tools like BloodHound have been updated to help visualize and detect these new attack vectors.
• Even with traditional network segmentation, attackers can exploit this overlooked vulnerability to compromise entire forests.

The Hidden Doorways Within Your Network

Imagine a sprawling corporate campus with dozens of buildings, each secured with its own locks and guards. But between those buildings, underground tunnels connect them all - tunnels that few know exist, and even fewer bother to check. In the world of Active Directory, these tunnels are called "Sites," and, as recent research reveals, attackers are learning to slip through them with alarming ease.

What Are Active Directory Sites - and Why Do They Matter?

Active Directory Sites were designed to make large, geographically spread-out networks run smoothly. By grouping together computers and servers that are physically close, Sites help manage network traffic and speed up authentication. But as security teams focused on obvious targets - like user accounts and domain controllers - Sites were left out of most security playbooks.

The oversight is now coming back to haunt organizations. Sites have their own permissions and access controls, which, if set up incorrectly, can let attackers jump from one part of a network to another, even across different domains within the same organization. It's like finding a master key hidden under the doormat.

How the Attack Works: Sidestepping the Sentries

According to a technical analysis by Quentin Roland, attackers exploit weak or misconfigured ACLs (access control lists) on Sites. By manipulating these settings and using clever tricks with Group Policy Objects (the rules that govern what users and computers can do), they can quietly escalate their privileges. Even security measures like SID filtering - meant to block cross-domain attacks - can be bypassed using these techniques.

Once inside, an attacker doesn't need to break through every door. Instead, they use the Sites' permissions to move laterally, sometimes gaining control over entire forests (collections of domains). The attack is especially effective because few security teams monitor or audit Site configurations regularly.

Lessons from the Past - and Tools for the Future

This isn't the first time overlooked AD features have led to major breaches. Past attacks, like the infamous Golden Ticket and ACL abuse scenarios, often succeeded because defenders underestimated the complexity of Active Directory's internal workings. Now, as attackers grow more sophisticated, even the most mundane network features can become high-value targets.

The good news: the community is responding. BloodHound, a popular tool for mapping attack paths, now includes features to track Site-related vulnerabilities. Organizations are urged to audit their Site configurations, review who can manage Site permissions, and keep defensive tools up to date. In an era where every corner of the network matters, ignoring Sites could be a costly mistake.

WIKICROOK

• Active Directory (AD): Active Directory (AD) is a Microsoft service that centralizes user access, authentication, and security policy management across computer networks.
• Active Directory Sites: Active Directory Sites group network locations to manage authentication and control traffic, improving efficiency in distributed or multi-location organizations.
• Access Control List (ACL): An Access Control List (ACL) is a set of rules that determines which users or systems can access specific digital resources and what actions they can perform.
• Group Policy Object (GPO): A Group Policy Object (GPO) is a set of rules in Active Directory that controls user and computer actions within a Windows network.
• BloodHound: BloodHound is a security tool that maps attack paths in Active Directory, enabling organizations to identify and remediate vulnerabilities in their networks.