Detection: Windows AD GPO New CSE Addition

Updated Date: 2023-11-22 ID: 700c11d1-da09-47b2-81aa-358c143c7986 Author: Dean Luxton Type: TTP Product: Splunk Enterprise Security

Description

This detection identifies when a a new client side extension is added to an Active Directory Group Policy using the Group Policy Management Console.

 1`wineventlog_security` EventCode=5136 ObjectClass=groupPolicyContainer AttributeLDAPDisplayName=gPCMachineExtensionNames 
 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_values>\{.*?\})" 
 5| rex field=ObjectDN max_match=10000 "CN=(?P<policy_guid>\{.*?\})" 
 6| mvexpand new_values 
 7| where NOT new_values IN (old_values,"{00000000-0000-0000-0000-000000000000}",policy_guid) AND match(new_values, "^\{[A-Z
 8|\d]+\-[A-Z
 9|\d]+\-[A-Z
10|\d]+\-[A-Z
11|\d]+\-[A-Z
12|\d]+\}") 
13| lookup msad_guid_lookup guid as new_values OUTPUTNEW displayName as policyType 
14| eval newPolicy=if(policyType like "%",policyType,new_values) 
15| join ObjectDN  [
16| search `admon` objectCategory="CN=Group-Policy-Container*" admonEventType=Update 
17| stats latest(displayName) as displayName by distinguishedName 
18| eval ObjectDN=upper(distinguishedName)] 
19| stats values(OpCorrelationID) as OpCorrelationID values(src_user) as src_user values(SubjectLogonId) as SubjectLogonId values(newPolicy) as newPolicy values(displayName) as policyName by ObjectDN 
20| `windows_ad_gpo_new_cse_addition_filter`

Data Source

Name Platform Sourcetype Source Supported App
N/A N/A N/A N/A N/A

Macros Used

Name Value
admon source=ActiveDirectory
windows_ad_gpo_new_cse_addition_filter search *
windows_ad_gpo_new_cse_addition_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
ID Technique Tactic
T1484 Domain or Tenant Policy Modification Defense Evasion
T1484.001 Group Policy Modification Privilege Escalation
T1222 File and Directory Permissions Modification Defense Evasion
T1222.001 Windows File and Directory Permissions Modification Privilege Escalation
KillChainPhase.EXPLOITAITON
NistCategory.DE_CM
Cis18Value.CIS_10
Cinnamon Tempest
Indrik Spider
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, admon data is also used to display the display name of the GPO. See lantern article in references for further on how to onboard AD audit data. Ensure the wineventlog_security and admon macros are configured with the correct indexes.

Known False Positives

General usage of group policy will trigger this detection, also please not GPOs modified using tools such as SharpGPOAbuse will not generate the AD audit events which enable this detection.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
$src_user$ has added new GPO Client Side Extensions $newPolicy$ to the policy $policyName$ 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: 1