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detections/application/windows_ad_dangerous_user_acl_modification.yml
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name: Windows AD Dangerous User ACL Modification | ||
id: ec5b6790-595a-4fb8-ad43-56e5b55a9617 | ||
version: 1 | ||
date: '2023-11-15' | ||
author: Dean Luxton | ||
status: production | ||
type: TTP | ||
data_source: | ||
- Windows Security 5136 | ||
description: User ACL modification event with potentially dangerous permissions applied. | ||
search: '`wineventlog_security` EventCode=5136 ObjectClass=user | ||
| eval old_value=if(OperationType=="%%14675",AttributeValue,null), new_value=if(OperationType=="%%14674",AttributeValue,null) | ||
| stats min(_time) as _time values(old_value) as old_value values(new_value) 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 msad_guid_lookup.csv guid as aceObjectGuid OUTPUT displayName as ControlAccessRights | ||
| lookup ace_access_rights_lookup.csv access_rights_string as AccessRights OUTPUT access_rights_value | ||
| lookup ace_type_lookup.csv ace_type_string as aceType OUTPUT ace_type_value as aceType | ||
| lookup ace_flag_lookup.csv 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.csv 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: See link in references for how to configure logging for these eventcodes. Include lookups for SID resolution if evt_resolve_ad_obj is set to 0. | ||
known_false_positives: Unknown | ||
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 | ||
tags: | ||
analytic_story: | ||
- Sneaky Active Directory Persistence Tricks | ||
asset_type: Endpoint | ||
confidence: 100 | ||
impact: 100 | ||
message: $src_user$ has added ACL rights to grant $user$ $aceControlAccessRights$ $aceAccessRights$ to user $ObjectDN$ | ||
mitre_attack_id: | ||
- T1484 | ||
- T1222 | ||
- T1222.001 | ||
observable: | ||
- name: user | ||
type: User | ||
role: | ||
- Victim | ||
- name: src_user | ||
type: User | ||
role: | ||
- Victim | ||
product: | ||
- Splunk Enterprise | ||
- Splunk Enterprise Security | ||
- Splunk Cloud | ||
risk_score: 100 | ||
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/DCShadowPermissions/windows-security-xml.log | ||
source: XmlWinEventLog:Security | ||
sourcetype: xmlwineventlog |
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