Windows AD Dangerous User ACL Modification
SPLUNK detection rule by Dean Luxton · Apache-2.0
This detection monitors the addition of the following ACLs to an Active Directory user object: "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". Such modifications can indicate potential privilege escalation or malicious activity. Immediate investigation is recommended upon alert.
name: Windows AD Dangerous User ACL Modification
id: ec5b6790-595a-4fb8-ad43-56e5b55a9617
version: 10
creation_date: '2024-07-01'
modification_date: '2026-05-13'
author: Dean Luxton
status: production
type: TTP
description: 'This detection monitors the addition of the following ACLs to an Active Directory user object: "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". Such modifications can indicate potential privilege escalation or malicious activity. Immediate investigation is recommended upon alert.'
data_source:
- Windows Event Log Security 5136
search: '`wineventlog_security` EventCode=5136 ObjectClass=user | 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 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_dangerous_user_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://learn.microsoft.com/en-us/windows/win32/secauthz/ace-strings
- https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-adts/1522b774-6464-41a3-87a5-1e5633c3fbbb
- https://trustedsec.com/blog/a-hitchhackers-guide-to-dacl-based-detections-part-1-a
- 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 ("$user$", "$src_user$") | 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: $src_user$ has added ACL rights to grant $user$ $aceControlAccessRights$ $aceAccessRights$ to user $ObjectDN$
entity:
field: src_user
type: user
score: 50
intermediate_findings:
entities:
- field: user
type: user
score: 50
message: $src_user$ has added ACL rights to grant $user$ $aceControlAccessRights$ $aceAccessRights$ to user $ObjectDN$
analytic_story:
- Sneaky Active Directory Persistence Tricks
asset_type: Endpoint
mitre_attack_id:
- T1222.001
- T1484
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/T1222.001/dacl_abuse/user_dacl_mod_windows-security-xml.log
source: XmlWinEventLog:Security
sourcetype: XmlWinEventLog
test_type: unit
CIRCL