Windows DCSync

👉 Overview

👀 What ?

Windows DCSync is a technique used by attackers to replicate domain controller account password hashes from Active Directory (AD). This technique exploits the replication capability of AD, which is designed to synchronize data across domain controllers. With DCSync, an attacker having necessary permissions can impersonate a domain controller and request account password information from the AD.

🧐 Why ?

Understanding Windows DCSync is crucial because it's a common technique used in cyber-attacks, especially in advanced persistent threats (APTs). It enables the attacker to gain unauthorized access to sensitive data and resources in an AD environment. Also, this technique often bypasses common security measures, making it a significant threat in the cybersecurity landscape.

⛏️ How ?

To use DCSync, the attacker must first gain sufficient permissions on the network, often via techniques like spear phishing or password cracking. Once the attacker has the necessary permissions, they can use tools like Mimikatz to perform DCSync attack. This involves making a request to the AD for password data of the target account, which is then replicated and sent back to the attacker.

⏳ When ?

DCSync attacks became widely recognized following their incorporation into the popular hacking tool Mimikatz in 2015. Since then, they have been used in several high-profile cyber-attacks, making them a significant area of focus for cybersecurity professionals.

⚙️ Technical Explanations

At a technical level, DCSync exploits the functionality of the Directory Replication Service (DRS) used by AD to synchronize data across domain controllers. By impersonating a domain controller, an attacker can make a DRSGetNCChanges request to the AD. This request is typically used to fetch changes made to an object in the AD database. However, when used maliciously, it can be used to retrieve password hashes of other AD accounts. The AD, believing the request to be legitimate, returns the requested data, which includes the NTLM hash of the target account's password. The attacker can then use this hash in pass-the-hash attacks to authenticate as the target user without needing to crack the password.