Windows AD Dangerous Deny ACL Modification

name: Windows AD Dangerous Deny ACL Modification
id: 8e897153-2ebd-4cb2-85d3-09ad57db2fb7
version: 8
date: '2026-03-10'
author: Dean Luxton
status: production
type: TTP
data_source:
    - Windows Event Log Security 5136
description: This detection identifies an Active Directory access-control list (ACL) modification event, which applies permissions that deny the ability to enumerate permissions of the object.
search: '`wineventlog_security` EventCode=5136 | 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 as aceType | 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 OUTPUT 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 values(aceType) as aceType values(aceFlags) as aceFlags values(aceControlAccessRights) as aceControlAccessRights values(aceAccessRights) as aceAccessRights values(new_ace) as new_ace values(aceInheritedTypeGuid) as aceInheritedTypeGuid by _time ObjectClass ObjectDN src_user SubjectLogonId user OpCorrelationID | eval aceControlAccessRights=if(mvcount(aceControlAccessRights)=1 AND aceControlAccessRights="","All rights",''aceControlAccessRights'') | search aceType IN ("Access denied",D) AND aceAccessRights IN ("Full control","Read permissions",RC) | `windows_ad_dangerous_deny_acl_modification_filter`'
how_to_implement: Ensure you are ingesting Active Directory audit logs - specifically event 5136. See lantern article in references for further on how to onboard AD audit data. Ensure the wineventlog_security macro is configured with the correct indexes and include lookups for SID resolution if evt_resolve_ad_obj is set to 0.
known_false_positives: No false positives have been identified at this time.
references:
    - https://happycamper84.medium.com/sneaky-persistence-via-hidden-objects-in-ad-1c91fc37bf54
    - https://www.youtube.com/watch?v=_nGpZ1ydzS8
    - 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$" and "$src_user$"
      search: '%original_detection_search% | search  user = "$user$" src_user = "$src_user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$user$" and "$src_user$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$", "$src_user$") starthoursago=168  | 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: $info_min_time$
      latest_offset: $info_max_time$
rba:
    message: $src_user$ has added ACL rights to deny $user$ $aceControlAccessRights$ $aceAccessRights$ to $ObjectDN$
    risk_objects:
        - field: user
          type: user
          score: 50
        - field: src_user
          type: user
          score: 50
    threat_objects: []
tags:
    analytic_story:
        - Sneaky Active Directory Persistence Tricks
    asset_type: Endpoint
    mitre_attack_id:
        - T1222.001
        - T1484
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1222.001/dacl_abuse/hidden_object_windows-security-xml.log
          source: XmlWinEventLog:Security
          sourcetype: XmlWinEventLog