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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.

  • Type: TTP

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2023-11-22
  • Author: Dean Luxton
  • ID: 700c11d1-da09-47b2-81aa-358c143c7986

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1484 Domain or Tenant Policy Modification Defense Evasion, Privilege Escalation
T1484.001 Group Policy Modification Defense Evasion, Privilege Escalation
T1222 File and Directory Permissions Modification Defense Evasion
T1222.001 Windows File and Directory Permissions Modification Defense Evasion
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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`wineventlog_security` EventCode=5136 ObjectClass=groupPolicyContainer AttributeLDAPDisplayName=gPCMachineExtensionNames 
| 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_values>\{.*?\})" 
| rex field=ObjectDN max_match=10000 "CN=(?P<policy_guid>\{.*?\})" 
| mvexpand new_values 
| where NOT new_values IN (old_values,"{00000000-0000-0000-0000-000000000000}",policy_guid) AND match(new_values, "^\{[A-Z
|\d]+\-[A-Z
|\d]+\-[A-Z
|\d]+\-[A-Z
|\d]+\-[A-Z
|\d]+\}") 
| lookup msad_guid_lookup guid as new_values OUTPUTNEW displayName as policyType 
| eval newPolicy=if(policyType like "%",policyType,new_values) 
| join ObjectDN  [
| search `admon` objectCategory="CN=Group-Policy-Container*" admonEventType=Update 
| stats latest(displayName) as displayName by distinguishedName 
| eval ObjectDN=upper(distinguishedName)] 
| 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 
| `windows_ad_gpo_new_cse_addition_filter`

Macros

The SPL above uses the following Macros:

:information_source: windows_ad_gpo_new_cse_addition_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Lookups

The SPL above uses the following Lookups:

Required fields

List of fields required to use this analytic.

  • _time
  • OperationType
  • ObjectDN
  • OpCorrelationID
  • src_user
  • AttributeLDAPDisplayName
  • AttributeValue
  • ObjectClass
  • SubjectLogonId
  • DSName

How To Implement

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

RBA

Risk Score Impact Confidence Message
100.0 100 100 $src_user$ has added new GPO Client Side Extensions $newPolicy$ to the policy $policyName$

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

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 | version: 1