Active Directory (AD) has become a prime target for cybercriminals, and a recent report sheds light on various attack strategies that exploit its vulnerabilities. Insights from this report highlight essential preventative measures for IT security teams.
Understanding Active Directory’s Role in Cybersecurity
Active Directory serves as the backbone of user authentication and resource access within Windows environments. According to Maulik Maheta, a Staff Research Scientist at Trellix, “In a Windows domain environment, Active Directory is the central nervous system that governs who can log in, what they can access, and how trust is enforced throughout the organization.” He emphasizes that compromising the NTDS.dit file essentially reveals the blueprint of the entire digital identity system.
The Risks of NTDS.dit Exposure
The NTDS.dit file, which contains a domain’s full directory database, is particularly crucial. It holds user accounts, group policies, computer objects, and the password hashes of all domain users, including those with elevated permissions like Domain Administrators. If attackers gain access to this file and the associated SYSTEM hive for decryption, they can extract password hashes, crack them offline, and impersonate users without needing to resort to phishing or other traditional attack modes. Maheta points out, “They now have the keys to the kingdom.” This makes NTDS.dit theft a significant risk, as it transforms data loss into identity theft at an infrastructure level.
Exploiting Active Directory: A Step-by-Step Breakdown
Maheta outlines a four-step framework frequently employed by attackers once they gain network access:
- The first move involves stealing password hashes, which can be done through methods like DCSync, extracting hashes from NTDS.dit, or capturing hashes from the lsass.exe process—an area where hashes of actively logged-in users are stored.
- Next, attackers often utilize the “Pass the Hash” technique, allowing them to authenticate as a legitimate user by using the stolen password hash. This can be as straightforward as launching cmd.exe with the hash or accessing network resources.
- With authenticated access, attackers can execute lateral movements within the network, leveraging tools like PSExec to run commands on remote systems. This maneuver amplifies their reach, leading to further credential theft across multiple systems.
- Should access be obtained to a domain controller’s file system, attackers can exfiltrate NTDS.dit alongside the HKEY_LOCAL_MACHINE\SYSTEM registry hive—the key to decrypting information in the file.
Although AD implements a file system lock on NTDS.dit to inhibit unauthorized copying, there are multiple strategies attackers can employ to bypass these barriers:
- Creating a snapshot of the volume using Volume Shadow Copy (VSS) and then extracting NTDS.dit from it.
- Utilizing PowerShell utilities to copy open files stealthily.
- Generating Active Directory installation media with built-in tools like DSDBUtil.exe or NTDSUtil.exe.
Maheta emphasizes that pilfering the NTDS.dit file goes beyond simple data theft; it results in a profound loss of identity, trust, and control within a Windows domain. The stealthy nature of these attacks poses another significant challenge, as attackers use common tools and subtle methods to avoid detection.
Enhancing Defense against AD Attacks
Trellix suggests that leveraging advanced detection systems can provide additional layers of protection against such threats. The Trellix NDR (Network Detection and Response) solution is designed to identify behavioral patterns and exfiltration attempts that conventional security measures might overlook. By focusing on subtle changes in activity, organizations can enhance their defenses against these evolving cyber threats.
