Detection: Windows AD Replication Request Initiated by User Account

Updated Date: 2025-03-27 ID: 51307514-1236-49f6-8686-d46d93cc2821 Author: Dean Luxton Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects a user account initiating an Active Directory replication request, indicative of a DCSync attack. It leverages EventCode 4662 from the Windows Security Event Log, focusing on specific object types and replication permissions. This activity is significant because it can allow an attacker with sufficient privileges to request password hashes for any or all users within the domain. If confirmed malicious, this could lead to unauthorized access, privilege escalation, and potential compromise of the entire domain.

 1`wineventlog_security` EventCode=4662 ObjectType IN ("%{19195a5b-6da0-11d0-afd3-00c04fd930c9}","domainDNS") 
 2    AND Properties IN ("*Replicating Directory Changes All*", "*{1131f6ad-9c07-11d1-f79f-00c04fc2dcd2}*","*{9923a32a-3607-11d2-b9be-0000f87a36b2}*","*{1131f6ac-9c07-11d1-f79f-00c04fc2dcd2}*")
 3    AND AccessMask="0x100" AND NOT (SubjectUserSid="NT AUT*" OR SubjectUserSid="S-1-5-18" OR SubjectDomainName="Window Manager" OR SubjectUserName="*$") 
 4
 5| stats min(_time) as _time, count by SubjectDomainName, SubjectUserName, Computer, Logon_ID, ObjectName, ObjectServer, ObjectType, OperationType, status dest 
 6| rename SubjectDomainName as Target_Domain, SubjectUserName as user, Logon_ID as TargetLogonId, _time as attack_time  
 7| appendpipe 
 8    [
 9| map search="search `wineventlog_security` EventCode=4624 TargetLogonId=$TargetLogonId$" 
10| fields - status] 
11
12| table attack_time, AuthenticationPackageName, LogonProcessName, LogonType, TargetUserSid, Target_Domain, user, Computer, TargetLogonId, status, src_ip, src_category, ObjectName, ObjectServer, ObjectType, OperationType, dest 
13| stats min(attack_time) as _time values(TargetUserSid) as TargetUserSid, values(Target_Domain) as Target_Domain, values(user) as user, values(Computer) as Computer, values(status) as status, values(src_category) as
14    src_category, values(src_ip) as src_ip by TargetLogonId dest
15
16| `windows_ad_replication_request_initiated_by_user_account_filter`

Data Source

Name Platform Sourcetype Source
Windows Event Log Security 4662 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Security'

Macros Used

Name Value
wineventlog_security eventtype="wineventlog_security" OR Channel="security" OR source="XmlWinEventLog:Security" OR source="WinEventLog:Security"
windows_ad_replication_request_initiated_by_user_account_filter search *
windows_ad_replication_request_initiated_by_user_account_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1003.006 DCSync Credential Access
Exploitation
DE.CM
CIS 10

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Notable Yes
Rule Title %name%
Rule Description %description%
Notable Event Fields user, dest
Creates Risk Event True
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

To successfully implement this search, you need to be ingesting eventcode 4662. The Advanced Security Audit policy settings Audit Directory Services Access within DS Access needs to be enabled, as well as the following SACLs applied to the domain root and all descendant objects. The principals everybody, Domain Computers, and Domain Controllers auditing the permissions Replicating Directory Changes, Replicating Directory Changes All, and Replicating Directory Changes In Filtered Set

Known False Positives

Azure AD Connect syncing operations and the dcdiag.exe /Test:Replications command.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

Windows Active Directory Replication Request Initiated by User Account $user$ from $src_ip$

Risk Object Risk Object Type Risk Score Threat Objects
user user 100 No Threat Objects
src_ip system 100 No Threat Objects

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset XmlWinEventLog:Security XmlWinEventLog
Integration ✅ Passing Dataset XmlWinEventLog:Security XmlWinEventLog

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 9