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
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
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Enable Auditing: Ensure Audit Directory Service Access is enabled on domain controllers.
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Collect Events: Gather Windows Event ID 4662 with AccessMask 0x100 (Control Access).
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Filter Replication GUIDs: Search for DS-Replication-Get-Changes and DS-Replication-Get-Changes-All.
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Identify Non-DC Sources: Flag events where SubjectUserName is not a domain controller machine account.
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Correlate with Network: Cross-reference source IPs against known DC addresses.
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Validate Findings: Exclude legitimate replication tools (Azure AD Connect, SCCM).
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Respond: Disable compromised accounts, reset krbtgt, investigate lateral movement.
Key Concepts
| Concept |
Description |
| DCSync |
Technique abusing AD replication protocol to extract password hashes |
| Event ID 4662 |
Directory Service Access audit event |
| DS-Replication-Get-Changes |
GUID 1131f6aa-9c07-11d1-f79f-00c04fc2dcd2 |
| DS-Replication-Get-Changes-All |
GUID 1131f6ad-9c07-11d1-f79f-00c04fc2dcd2 |
| AccessMask 0x100 |
Control Access right indicating extended rights verification |
| T1003.006 |
OS Credential Dumping: DCSync |
Tools & Systems
| Tool |
Purpose |
| Windows Event Viewer |
Direct event log analysis |
| Splunk |
SIEM correlation of Event 4662 |
| Elastic Security |
Detection rules for DCSync patterns |
| Mimikatz lsadump::dcsync |
Attack tool used to perform DCSync |
| Impacket secretsdump.py |
Python-based DCSync implementation |
| BloodHound |
Identify accounts with replication rights |
Output Format
Hunt ID: TH-DCSYNC-[DATE]-[SEQ]
Technique: T1003.006
Domain Controller: [DC hostname]
Subject Account: [Account performing replication]
Source IP: [Non-DC IP address]
GUID Accessed: [Replication GUID]
Risk Level: [Critical/High/Medium/Low]
Recommended Action: [Disable account, reset krbtgt, investigate]
