hunting-for-dcsync-attacks

Detect DCSync attacks by analyzing Windows Event ID 4662 for unauthorized DS-Replication-Get-Changes requests from non-domain-controller accounts.

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Repository: xalgord/xalgorix
Last source activity: June 6, 2026 at 16:41
Detected SKILL.md language: English
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Forks: 146

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Hunting for DCSync Attacks

When to Use

When hunting for DCSync credential theft (MITRE ATT&CK T1003.006)

After detecting Mimikatz or similar tools in the environment

During incident response involving Active Directory compromise

When monitoring for unauthorized domain replication requests

During purple team exercises testing AD attack detection

Detection Gaps & Validation

No SACL = no telemetry. Event 4662 is only generated if "Audit Directory Service Access" is enabled AND the domain object's SACL audits the replication extended rights. Without both, DCSync is completely invisible — verify the SACL before trusting a "clean" result.

Both GUIDs matter: flag DS-Replication-Get-Changes (1131f6aa-9c07-11d1-f79f-00c04fc2dcd2) AND DS-Replication-Get-Changes-All (1131f6ad-...). Get-Changes-All is the strong signal; Get-Changes alone can be benign.

Source-based detection blind spots: an attacker running from a real DC or relaying a DC machine account won't trip the "non-DC source" filter.

Validate the hunt fires: run mimikatz lsadump::dcsync /user:krbtgt or Impacket secretsdump.py -just-dc from a non-DC host; confirm 4662 with AccessMask 0x100 and the replication GUID appears and your rule alerts.

FP tuning: legitimate DCs replicating, Azure AD Connect / Entra Connect (MSOL_ / AAD_ accounts), some backup/migration tools. Whitelist by exact account and source IP, never by name substring alone.

Prerequisites

Windows Security Event Log forwarding enabled (Event ID 4662)

Audit Directory Service Access enabled via Group Policy

Domain Computers SACL configured on Domain Object for machine account detection

SIEM with Windows event data ingested (Splunk, Elastic, Sentinel)

Knowledge of legitimate domain controller accounts and replication partners

Workflow

Enable Auditing: Ensure Audit Directory Service Access is enabled on domain controllers.

Collect Events: Gather Windows Event ID 4662 with AccessMask 0x100 (Control Access).

Filter Replication GUIDs: Search for DS-Replication-Get-Changes and DS-Replication-Get-Changes-All.

Identify Non-DC Sources: Flag events where SubjectUserName is not a domain controller machine account.