Windows AD AdminSDHolder ACL Modified

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Description

The following analytic detects modifications to the Access Control List (ACL) of the AdminSDHolder object in a Windows domain, specifically the addition of new rules. It leverages EventCode 5136 from the Security Event Log, focusing on changes to the nTSecurityDescriptor attribute. This activity is significant because the AdminSDHolder object secures privileged group members, and unauthorized changes can allow attackers to establish persistence and escalate privileges. If confirmed malicious, this could enable an attacker to control domain-level permissions, compromising the entire Active Directory environment.

• Type: TTP

• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

• Last Updated: 2024-05-13
• Author: Mauricio Velazco, Splunk
• ID: 00d877c3-7b7b-443d-9562-6b231e2abab9

Annotations

ATT&CK

ATT&CK

ID	Technique	Tactic
T1546	Event Triggered Execution	Privilege Escalation, Persistence

Kill Chain Phase

• Exploitation
• Installation

NIST

• DE.CM

CIS20

• CIS 10

CVE

Search

 `wineventlog_security` EventCode=5136 AttributeLDAPDisplayName=nTSecurityDescriptor OperationType="%%14674" ObjectDN="CN=AdminSDHolder,CN=System*" 
| rex field=AttributeValue max_match=10000 "A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;(?P<added_user_sid>S-1-[0-59]-\d{2}-\d{8,10}-\d{8,10}-\d{8,10}-[1-9]\d{3})\)" 
| stats values(added_user_sid) by _time, Computer, SubjectUserName, ObjectDN 
| `windows_ad_adminsdholder_acl_modified_filter`

Macros

The SPL above uses the following Macros:

• wineventlog_security

windows_ad_adminsdholder_acl_modified_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

• _time
• EventCode
• AttributeLDAPDisplayName
• OperationType
• ObjectDN
• Computer
• SubjectUserName
• AttributeValue

How To Implement

To successfully implement this search, you ned to be ingesting eventcode 5136. The Advanced Security Audit policy setting Audit Directory Services Changes within DS Access needs to be enabled. Additionally, a SACL needs to be created for the AdminSDHolder object in order to log modifications.

Known False Positives

Adding new users or groups to the AdminSDHolder ACL is not usual. Filter as needed

Associated Analytic Story

• Sneaky Active Directory Persistence Tricks

RBA

Risk Score	Impact	Confidence	Message
56.0	80	70	The AdminSDHolder domain object has been modified on $Computer$ by $SubjectUserName$

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

• https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/plan/security-best-practices/appendix-c–protected-accounts-and-groups-in-active-directory
• https://social.technet.microsoft.com/wiki/contents/articles/22331.adminsdholder-protected-groups-and-security-descriptor-propagator.aspx
• https://adsecurity.org/?p=1906
• https://pentestlab.blog/2022/01/04/domain-persistence-adminsdholder/
• https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-5136
• https://learn.microsoft.com/en-us/windows/win32/secauthz/access-control-lists
• https://medium.com/@cryps1s/detecting-windows-endpoint-compromise-with-sacls-cd748e10950

Test Dataset

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

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