splunk-security_content/detections/application/windows_ad_self_dacl_assignment.yml

name: Windows AD Self DACL Assignment
id: 16132445-da9f-4d03-ad44-56d717dcd67d
version: 2
date: '2024-09-30'
author: Dean Luxton
status: production
type: TTP
data_source:
- Windows Security 5136
description: Detect when a user creates a new DACL in AD for their own AD 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 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 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  | lookup ace_access_rights_lookup access_rights_string as AccessRights OUTPUT access_rights_value  | lookup msad_guid_lookup guid as aceObjectGuid OUTPUT displayName as ControlAccessRights ``` 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), aceInheritance=coalesce(ace_flag_value,"This object only"), aceAccessRights=if(aceAccessRights="CCDCLCSWRPWPDTLOCRSDRCWDWO","Full control",coalesce(access_rights_value,AccessRights)), aceControlAccessRights=if((ControlAccessRights="Write member" OR aceObjectGuid="bf9679c0-0de6-11d0-a285-00aa003049e2") AND (aceAccessRights="All validated writes" OR AccessRights="SW"),"Add/remove self as member",coalesce(ControlAccessRights,aceObjectGuid)), user=coalesce(user, group, builtin_group, aceSid)  | stats values(aceType) as aceType values(aceInheritance) as aceInheritance 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'') | rex field=user "\\\(?P<nt_user>.*?)$" | where lower(src_user)=lower(nt_user) | `windows_ad_self_dacl_assignment_filter`'
how_to_implement: Ensure you are ingesting Active Directory audit logs - specifically event 5136. See lantern article in references for further on how to onboard AD audit data. Ensure the wineventlog_security macro is configured with the correct indexes and include lookups for SID resolution if evt_resolve_ad_obj is set to 0.
known_false_positives: Unknown
references:
- https://lantern.splunk.com/Security/Product_Tips/Enterprise_Security/Enabling_an_audit_trail_from_Active_Directory
drilldown_searches:
- name: View the detection results for - "$src_user$"
  search: '%original_detection_search% | search  src_user = "$src_user$"'
  earliest_offset: $info_min_time$
  latest_offset: $info_max_time$
- name: View risk events for the last 7 days for - "$src_user$"
  search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$src_user$") 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: $info_max_time$
tags:
  analytic_story:
  - Sneaky Active Directory Persistence Tricks
  asset_type: Endpoint
  confidence: 100
  impact: 80
  message: $src_user$ has created a DACL on $ObjectDN$ to grant themselves $aceControlAccessRights$ across $aceAccessRights$
  mitre_attack_id:
  - T1484
  - T1098
  observable:
  - name: src_user
    type: User
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  risk_score: 80
  required_fields:
  - _time
  - OperationType
  - ObjectDN
  - OpCorrelationID
  - src_user
  - AttributeLDAPDisplayName
  - AttributeValue
  - ObjectClass
  - SubjectLogonId
  - DSName
  security_domain: endpoint
tests:
- name: True Positive Test
  attack_data:
  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1484/aclmodification/windows-security-xml.log
    source: XmlWinEventLog:Security
    sourcetype: xmlwineventlog