ID | Technique | Tactic |
---|---|---|
T1484 | Domain or Tenant Policy Modification | Defense Evasion |
T1207 | Rogue Domain Controller | Privilege Escalation |
T1222.001 | Windows File and Directory Permissions Modification | Defense Evasion |
Detection: Windows AD DCShadow Privileges ACL Addition
Description
This detection identifies an Active Directory access-control list (ACL) modification event, which applies the minimum required extended rights to perform the DCShadow attack.
Search
1`wineventlog_security` EventCode=5136 ObjectClass=domainDNS
2| 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
3| rex field=old_value max_match=10000 "\((?P<old_values>.*?)\)"
4| rex field=new_value max_match=10000 "\((?P<new_ace>.*?)\)"
5| mvexpand new_ace
6| where NOT new_ace IN (old_values)
7| rex field=new_ace "(?P<aceType>.*?);(?P<aceFlags>.*?);(?P<aceAccessRights>.*?);(?P<aceObjectGuid>.*?);;(?P<aceSid>.*?)$"
8| search aceObjectGuid IN ("9923a32a-3607-11d2-b9be-0000f87a36b2","1131f6ab-9c07-11d1-f79f-00c04fc2dcd2","1131f6ac-9c07-11d1-f79f-00c04fc2dcd2")
9| rex max_match=100 field=aceAccessRights "(?P<AccessRights>[A-Z]{2})"
10| rex max_match=100 field=aceFlags "(?P<aceFlags>[A-Z]{2})"
11| lookup msad_guid_lookup guid as aceObjectGuid OUTPUT displayName as ControlAccessRights
12| lookup ace_access_rights_lookup access_rights_string as AccessRights OUTPUT access_rights_value
13| lookup ace_type_lookup ace_type_string as aceType OUTPUT ace_type_value
14| lookup ace_flag_lookup flag_string as aceFlags OUTPUT flag_value as ace_flag_value ``` Optional SID resolution lookups
15| lookup identity_lookup_expanded objectSid as aceSid OUTPUT downLevelDomainName as user
16| lookup admon_groups_def objectSid as aceSid OUTPUT cn as group ```
17| lookup builtin_groups_lookup builtin_group_string as aceSid OUTPUT builtin_group_name as builtin_group
18| 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)
19| 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
20| search (aceControlAccessRights="Add/Remove Replica In Domain" AND aceControlAccessRights="Manage Replication Topology" AND aceControlAccessRights="Replication Synchronization") OR (aceControlAccessRights="9923a32a-3607-11d2-b9be-0000f87a36b2" AND aceControlAccessRights="1131f6ab-9c07-11d1-f79f-00c04fc2dcd2" AND aceControlAccessRights="1131f6ac-9c07-11d1-f79f-00c04fc2dcd2")
21| `windows_ad_dcshadow_privileges_acl_addition_filter`
Data Source
Name | Platform | Sourcetype | Source | Supported App |
---|---|---|---|---|
N/A | N/A | N/A | N/A | N/A |
Macros Used
Name | Value |
---|---|
wineventlog_security | eventtype=wineventlog_security OR Channel=security OR source=XmlWinEventLog:Security |
windows_ad_dcshadow_privileges_acl_addition_filter | search * |
windows_ad_dcshadow_privileges_acl_addition_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
Default Configuration
This detection is configured by default in Splunk Enterprise Security to run with the following settings:
Setting | Value |
---|---|
Disabled | true |
Cron Schedule | 0 * * * * |
Earliest Time | -70m@m |
Latest Time | -10m@m |
Schedule Window | auto |
Creates Notable | Yes |
Rule Title | %name% |
Rule Description | %description% |
Notable Event Fields | user, dest |
Creates Risk Event | True |
Implementation
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
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
ACL modification Event Initiated by $src_user$ applying $user$ the minimum required extended rights to perform a DCShadow attack. | 100 | 100 | 100 |
References
-
https://www.labofapenetrationtester.com/2018/04/dcshadow.html
-
https://github.com/samratashok/nishang/blob/master/ActiveDirectory/Set-DCShadowPermissions.ps1
-
https://trustedsec.com/blog/a-hitchhackers-guide-to-dacl-based-detections-part-1-a
Detection Testing
Test Type | Status | Dataset | Source | Sourcetype |
---|---|---|---|---|
Validation | ✅ Passing | N/A | N/A | N/A |
Unit | ✅ Passing | Dataset | XmlWinEventLog:Security |
xmlwineventlog |
Integration | ✅ Passing | Dataset | XmlWinEventLog:Security |
xmlwineventlog |
Replay any dataset to Splunk Enterprise by using our replay.py
tool or the UI.
Alternatively you can replay a dataset into a Splunk Attack Range
Source: GitHub | Version: 1