detecting-dcsync-attack-in-active-directory

name	detecting-dcsync-attack-in-active-directory
description	Detect DCSync attacks where adversaries abuse Active Directory replication privileges to extract password hashes by monitoring for non-domain-controller accounts requesting directory replication via DsGetNCChanges.
domain	cybersecurity
subdomain	threat-hunting
tags	["threat-hunting","active-directory","dcsync","credential-theft","mitre-t1003-006","mimikatz","kerberos"]
version	1.0
author	mahipal
license	Apache-2.0
d3fend_techniques	["Application Protocol Command Analysis","Network Isolation","Network Traffic Analysis","Client-server Payload Profiling","Platform Monitoring"]
nist_csf	["DE.CM-01","DE.AE-02","DE.AE-07","ID.RA-05"]

Detecting DCSync Attack in Active Directory

When to Use

• When hunting for credential theft in Active Directory environments
• After compromise of accounts with Replicating Directory Changes permissions
• When investigating suspected use of Mimikatz or Impacket secretsdump
• During incident response involving lateral movement with domain admin credentials
• When auditing AD replication permissions as part of security hardening

Prerequisites

• Windows Security Event Logs with Event ID 4662 (Object Access) enabled
• Advanced Audit Policy: Audit Directory Service Access enabled
• Domain Controller event forwarding to SIEM
• Knowledge of legitimate domain controller hostnames and IPs
• Directory Service Access auditing with SACL on domain object

Workflow

1. Identify Legitimate Replication Sources: Document all domain controllers in the environment by hostname, IP, and computer account. Only these should perform directory replication.
2. Enable Required Auditing: Configure Advanced Audit Policy to capture Event ID 4662 on domain controllers with specific GUID monitoring for replication rights.
3. Monitor Replication Rights Access: Track access to three critical GUIDs -- DS-Replication-Get-Changes (1131f6aa-9c07-11d1-f79f-00c04fc2dcd2), DS-Replication-Get-Changes-All (1131f6ad-9c07-11d1-f79f-00c04fc2dcd2), and DS-Replication-Get-Changes-In-Filtered-Set (89e95b76-444d-4c62-991a-0facbeda640c).
4. Detect Non-DC Replication Requests: Alert when any account NOT associated with a domain controller requests replication rights.
5. Correlate with Network Traffic: DCSync generates replication traffic (MS-DRSR/RPC) from the attacker's machine to the DC. Monitor for DrsGetNCChanges RPC calls from non-DC IP addresses.
6. Investigate Source Context: Examine the process, user account, and machine originating the replication request.
7. Check for Credential Abuse: After DCSync detection, audit for subsequent use of extracted hashes (pass-the-hash, golden ticket creation).

Key Concepts

Concept	Description
T1003.006	OS Credential Dumping: DCSync
DCSync	Mimicking domain controller replication to extract credentials
DsGetNCChanges	RPC function used to request AD replication data