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Description

The following analytic identifies the modification of the Access Control List for the AdminSDHolder object within a Windows domain. Specifically, the detection triggers on the addition of a new rule to the existing ACL. AdminSDHolder is an object located in the System Partition in Active Directory and is used as a security template for objects that are members of certain privileged groups. Objects in these groups are enumerated and any objects with security descriptors that dont match the AdminSDHolder ACL are flagged for updating. The Security Descriptor propagator (SDProp) process runs every 60 minutes on the PDC Emulator and re-stamps the object Access Control List (ACL) with the security permissions set on the AdminSDHolder. An adversary who has obtained privileged access to a Windows Domain may modify the AdminSDHolder ACL to establish persistence and allow an unprivileged user to take control of a domain.

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

  • Last Updated: 2022-11-15
  • 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
1
2
3
4
 `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:

:information_source: 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

RBA

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

:information_source: 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

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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