Qilin ransomware operators are now using DCSync attacks—a technique that abuses Windows Active Directory's built-in replication protocol—to extract domain credentials without deploying malware on victim networks. This method, documented in attacks throughout H1 2026, allows attackers who have already gained network access to harvest the password hashes of every user and machine in an enterprise, enabling persistent control and lateral movement across entire organizations.
The adoption of DCSync by Qilin marks a shift toward credential-based attacks that exploit legitimate system functionality rather than relying on malware deployment. According to Group-IB's research of a documented H1 2026 intrusion, attackers used Mimikatz to conduct the replication attacks directly from domain controllers. This approach is particularly dangerous because it leaves fewer traces than traditional malware-based intrusions and gives defenders a narrow window to detect anomalous replication activity before attackers escalate.
Table of Contents
- How DCSync Abuses Active Directory Replication
- A Real Attack: Detection Through Anomalous Replication
- Scale and Targeting: Who Qilin Is Attacking
- Why DCSync Is Hard to Detect
- How to Detect and Stop DCSync Attacks
- Practical Next Steps for Your Organization
- Frequently Asked Questions
How DCSync Abuses Active Directory Replication
DCSync exploits the Directory Replication Service Remote Protocol (MS-DRSR), a legitimate Windows feature that domain controllers use to synchronize user and machine data with each other. When an attacker obtains credentials with Replicating Directory Changes permissions—often through initial compromise—they can impersonate a domain controller and request a full directory synchronization, pulling every password hash, including the critical KRBTGT account hash, without triggering typical malware detection.
According to Cybersecurity News, the technique requires minimal additional attack infrastructure. Once attackers hold the KRBTGT hash, they can forge Ticket Granting Tickets (Golden Tickets) to maintain persistent, near-permanent control over the entire Active Directory domain. This means an attacker can create fake login credentials that never expire and bypass most authentication checks, even after passwords are reset.
A Real Attack: Detection Through Anomalous Replication
In the documented H1 2026 intrusion, Qilin's replication activity left detectable traces. Cybersecurity News reported that anomalous replication was logged under the built-in Administrator account, which has no legitimate business performing bulk directory replication.
The forensic evidence showed hundreds of Event ID 4662 audit entries—a Directory service Access event that flags replication requests—at timestamps 01:19, 01:21, and 01:23, revealing the exact timing window of the attack. This case illustrates that DCSync attacks do generate audit logs, but they must be actively monitored. Many organizations leave Directory Service Access auditing disabled or do not correlate these events with SIEM tools, allowing the attack to proceed undetected during the critical early stages.
Scale and Targeting: Who Qilin Is Attacking
Qilin's adoption of DCSync has coincided with explosive growth. Between July 2025 and June 2026, Qilin claimed 1,403 victims globally, averaging 117 compromised organizations monthly, with H1 2026 alone showing 443% year-over-year growth in victim claims. The geographic concentration is striking: North America accounts for 53.9% of Qilin's 2026 victims, making U.S.
and Canadian organizations the primary targets. Manufacturing and construction sectors are bearing the largest burden, likely because these industries combine valuable data, legacy systems, and operational technology that is difficult to quickly recover. healthcare and professional services also rank high among targeted sectors. Qilin now operates a mature affiliate-based business model offering 80–85% ransom payouts to incentivize distribution, meaning the threat is not concentrated in one attack group but distributed across a network of criminal partners.
Why DCSync Is Hard to Detect
A central challenge is that DCSync uses legitimate Active Directory replication functionality. According to SentinelOne, this makes it difficult to distinguish from normal synchronization operations like Microsoft Entra Connect, the cloud sync service many organizations run. A security team observing replication traffic may initially assume it is routine directory maintenance rather than a breach in progress.
The attack also has a prerequisite: the attacker must already possess credentials with Replicating Directory Changes permissions. This means DCSync is typically a second-stage or third-stage attack, arriving after the attacker has already achieved initial access through phishing, credential theft, or exploitation of internet-facing systems. By the time replication activity begins, the attacker has already crossed the perimeter.
How to Detect and Stop DCSync Attacks
Microsoft's recommended defense strategy focuses on four key actions: resetting the KRBTGT password twice annually, tightly restricting Replicating Directory Changes permissions, enabling Directory Service Access auditing (Event ID 4662), and implementing SIEM correlation rules to flag replication from non-domain-controller accounts. Each step addresses a different layer of the attack chain.
Start with detection: enable Event ID 4662 logging and configure your SIEM to alert when replication requests originate from accounts that are not domain controllers or known backup/sync systems. Restrict the Replicating Directory Changes permission to only the accounts that genuinely need it—typically only domain controllers and dedicated sync service accounts. For defense depth, reset the KRBTGT password on a schedule; even if attackers harvest old hashes, regular rotation forces them to conduct new DCSync attacks to refresh their access.
Practical Next Steps for Your Organization
If your organization has not already, audit which accounts hold Replicating Directory Changes permissions—you may find legacy sync accounts or service accounts that no longer serve a purpose. Document the legitimate replication sources in your environment (domain controllers, Microsoft Entra Connect servers, backup systems) so you can configure your monitoring to flag exceptions immediately. Ensure your backup of Active Directory is isolated and restorable; if you are compromised via DCSync, a clean AD restore is your fastest recovery path.
Test your Event ID 4662 logging and SIEM alerting now, in a non-critical window. Many organizations discover during an incident that these logs were not being collected or that alerts were misconfigured. If you do not have a SIEM, even basic script-based monitoring of Event Viewer on your domain controllers can catch high-volume replication requests outside business hours. The goal is not perfection; it is reducing the time between when an attacker executes DCSync and when your team detects it.
Frequently Asked Questions
What if an attacker already has my KRBTGT hash from a DCSync attack?
Reset the KRBTGT password immediately (twice, because the previous hash remains valid for a period). This invalidates forged Golden Tickets created with the old hash. You should also force a password reset across all user accounts and monitor for unusual authentication activity in the 30 days following the attack.
Do I need to shut down Active Directory replication to stop DCSync?
No. DCSync exploits legitimate replication, but you prevent it by controlling who has permission to request replication (restrict Replicating Directory Changes) and by monitoring when replication occurs. The goal is not to disable the feature but to make it impossible for an attacker to abuse it without immediate detection.
How do I know if DCSync was used against me if I was already breached?
Request Event ID 4662 logs from your domain controllers covering the suspected breach window. Look for replication requests (Directory Service Access events) from the built-in Administrator account or service accounts that should not be syncing directory data. Group-IB and Cybersecurity News both provide IOC guidance for identifying these signatures in your logs.