Windows AD AdminSDHolder ACL Modified

name: Windows AD AdminSDHolder ACL Modified
id: 00d877c3-7b7b-443d-9562-6b231e2abab9
version: 11
creation_date: '2022-11-15'
modification_date: '2026-05-13'
author: Mauricio Velazco, Dean Luxton, Splunk
status: production
type: TTP
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.
data_source:
    - Windows Event Log Security 5136
search: '`wineventlog_security` EventCode=5136 ObjectClass=container ObjectDN="CN=AdminSDHolder,CN=System*"  | stats min(_time) as _time values(eval(if(OperationType=="%%14675",AttributeValue,null))) as old_value values(eval(if(OperationType=="%%14674",AttributeValue,null))) as new_value values(OperationType) as OperationType values(dest) as dest by ObjectClass ObjectDN OpCorrelationID src_user SubjectLogonId  | rex field=old_value max_match=10000 "\((?P<old_values>.*?)\)"  | rex field=new_value max_match=10000 "\((?P<new_ace>.*?)\)"  | mvexpand new_ace | where NOT new_ace IN (old_values)  | rex field=new_ace "(?P<aceType>.*?);(?P<aceFlags>.*?);(?P<aceAccessRights>.*?);(?P<aceObjectGuid>.*?);(?P<aceInheritedTypeGuid>.*?);(?P<aceSid>.*?)$" | rex max_match=100 field=aceAccessRights "(?P<AccessRights>[A-Z]{2})"  | rex max_match=100 field=aceFlags "(?P<aceFlags>[A-Z]{2})"  | lookup msad_guid_lookup guid as aceObjectGuid OUTPUT displayName as ControlAccessRights | lookup ace_access_rights_lookup access_rights_string as AccessRights OUTPUT access_rights_value  | lookup ace_type_lookup ace_type_string as aceType OUTPUT ace_type_value  | lookup ace_flag_lookup flag_string as aceFlags OUTPUT flag_value as ace_flag_value ``` Optional SID resolution lookups | lookup identity_lookup_expanded objectSid as aceSid OUTPUT downLevelDomainName as user  | lookup admon_groups_def objectSid as aceSid OUTPUT cn as group``` | lookup builtin_groups_lookup builtin_group_string  as aceSid OUTPUTNEW builtin_group_name as builtin_group | eval aceType=coalesce(ace_type_value,aceType), aceFlags=coalesce(ace_flag_value,"This object only"), aceAccessRights=if(aceAccessRights="CCDCLCSWRPWPDTLOCRSDRCWDWO","Full control",coalesce(access_rights_value,AccessRights)), aceControlAccessRights=coalesce(ControlAccessRights,aceObjectGuid), user=coalesce(user, group, builtin_group, aceSid) | stats min(_time) as _time values(aceType) as aceType values(aceFlags) as aceFlags(inheritance) values(aceControlAccessRights) as aceControlAccessRights values(aceAccessRights) as aceAccessRights values(new_ace) as new_ace values(SubjectLogonId) as SubjectLogonId by ObjectClass ObjectDN src_user user | eval aceControlAccessRights=if(mvcount(aceControlAccessRights)=1 AND aceControlAccessRights="","All rights",''aceControlAccessRights'') | search NOT aceType IN (*denied*,D,OD,XD) AND aceAccessRights IN ("Full control","All extended rights","All validated writes","Create all child objects","Delete all child objects","Delete subtree","Delete","Modify permissions","Modify owner","Write all properties",CC,CR,DC,DT,SD,SW,WD,WO,WP) | `windows_ad_adminsdholder_acl_modified_filter`'
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
references:
    - 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
    - https://lantern.splunk.com/Security/Product_Tips/Enterprise_Security/Enabling_an_audit_trail_from_Active_Directory
drilldown_searches:
    - name: View the detection results for - "$user$"
      search: '%original_detection_search% | search  user = "$user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$user$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
finding:
    title: The AdminSDHolder domain object $ObjectDN$ has been modified by $src_user$
    entity:
        field: src_user
        type: user
        score: 50
intermediate_findings:
    entities:
        - field: user
          type: user
          score: 50
          message: The AdminSDHolder domain object $ObjectDN$ has been modified by $src_user$
analytic_story:
    - Sneaky Active Directory Persistence Tricks
asset_type: Endpoint
mitre_attack_id:
    - T1546
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1546/adminsdholder_modified/windows-security.log
          source: XmlWinEventLog:Security
          sourcetype: XmlWinEventLog
      test_type: unit