| ID | Technique | Tactic |
|---|---|---|
| T1484 | Domain or Tenant Policy Modification | Defense Evasion |
| T1222 | File and Directory Permissions Modification | Privilege Escalation |
| T1222.001 | Windows File and Directory Permissions Modification | Defense Evasion |
Detection: Windows AD Hidden OU Creation
Description
This analytic is looking for when an ACL is applied to an OU which denies listing the objects residing in the OU. This activity combined with modifying the owner of the OU will hide AD objects even from domain administrators.
Search
1`wineventlog_security` EventCode=5136 ObjectClass=organizationalUnit
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<aceInheritedTypeGuid>.*?);(?P<aceSid>.*?)$"
8| rex max_match=100 field=aceAccessRights "(?P<AccessRights>[A-Z]{2})"
9| rex max_match=100 field=aceFlags "(?P<aceFlags>[A-Z]{2})"
10| lookup msad_guid_lookup guid as aceObjectGuid OUTPUT displayName as ControlAccessRights
11| lookup ace_access_rights_lookup access_rights_string as AccessRights OUTPUT access_rights_value
12| lookup ace_type_lookup ace_type_string as aceType OUTPUT ace_type_value as aceType
13| lookup ace_flag_lookup flag_string as aceFlags OUTPUT flag_value as ace_flag_value ``` Optional SID resolution lookups
14| lookup identity_lookup_expanded objectSid as aceSid OUTPUT downLevelDomainName as user
15| lookup admon_groups_def objectSid as aceSid OUTPUT cn as group ```
16| lookup builtin_groups_lookup builtin_group_string as aceSid OUTPUT builtin_group_name as builtin_group
17| 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)
18| 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
19| eval aceControlAccessRights=if(mvcount(aceControlAccessRights)=1 AND aceControlAccessRights="","All rights",'aceControlAccessRights')
20| search aceType IN ("Access denied",D) AND aceAccessRights IN ("List contents","List objects",LC,LO)
21| `windows_ad_hidden_ou_creation_filter`
Data Source
No data sources specified for this detection.
Macros Used
| Name | Value |
|---|---|
| wineventlog_security | eventtype=wineventlog_security OR Channel=security OR source=XmlWinEventLog:Security |
| windows_ad_hidden_ou_creation_filter | search * |
windows_ad_hidden_ou_creation_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
MITRE ATT&CK
Kill Chain Phases
NIST
CIS
Threat Actors
KillChainPhase.EXPLOITAITON
NistCategory.DE_CM
Cis18Value.CIS_10
Wizard Spider
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 |
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.
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
None.
Associated Analytic Story
Risk Based Analytics (RBA)
| Risk Message | Risk Score | Impact | Confidence |
|---|---|---|---|
| $src_user$ has hidden the contents of OU $ObjectDN$ from $user$ | 100 | 100 | 100 |
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
References
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: 2