Detection: Windows Default Group Policy Object Modified

Updated Date: 2026-05-13 ID: fe6a6cc4-9e0d-4d66-bcf4-2c7f44860876 Author: Mauricio Velazco, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects modifications to default Group Policy Objects (GPOs) using Event ID 5136. It monitors changes to the Default Domain Controllers Policy and Default Domain Policy, which are critical for enforcing security settings across domain controllers and all users/computers, respectively. This activity is significant because unauthorized changes to these GPOs can indicate an adversary with privileged access attempting to deploy persistence mechanisms or execute malware across the network. If confirmed malicious, such modifications could lead to widespread compromise, allowing attackers to maintain control and execute arbitrary code on numerous hosts.

Search

 1`wineventlog_security` EventCode=5136 ObjectClass=groupPolicyContainer AttributeLDAPDisplayName=versionNumber (ObjectDN="CN={31B2F340-016D-11D2-945F-00C04FB984F9},CN=POLICIES,CN=SYSTEM,DC=*" OR ObjectDN="CN={6AC1786C-016F-11D2-945F-00C04fB984F9},CN=POLICIES,CN=SYSTEM,DC=*")
 2  
 3| stats min(_time) as firstTime max(_time) as lastTime
 4    BY ObjectDN SubjectUserSid AttributeValue
 5       Computer DSName dest
 6  
 7| rename AttributeValue as versionNumber
 8  
 9| `security_content_ctime(firstTime)`
10  
11| `security_content_ctime(lastTime)`
12  
13| `windows_default_group_policy_object_modified_filter`

Data Source

Name	Platform	Sourcetype	Source
Windows Event Log Security 5136	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Security'`

Macros Used

Name	Value
wineventlog_security	`eventtype="wineventlog_security" OR Channel="security" OR source="XmlWinEventLog:Security" OR source="WinEventLog:Security"`
windows_default_group_policy_object_modified_filter	`search *`

windows_default_group_policy_object_modified_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
T1484.001	Group Policy Modification	Defense Impairment

Exploitation

DE.CM

CIS 10

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 Finding (Notable)	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Intermediate Finding (Risk Event)	Yes

TTP detections generate a Finding (Notable) and may generate Intermediate Findings (Risk Events) for associated entities.

Implementation

To successfully implement this search, the Advanced Security Audit policy setting Audit Directory Service Changes within DS Access needs to be enabled. Furthermore, the appropriate system access control lists (SACL) need to be created as the used events are not logged by default. A good guide to accomplish this can be found here https://jgspiers.com/audit-group-policy-changes/.

Known False Positives

The default Group Policy Objects within an AD network may be legitimately updated for administrative operations, filter as needed.

Associated Analytic Story

Finding

Title	Entity Field	Entity Type	Risk Score
A default group policy object was modified on $Computer$ by $SubjectUserSid$	SubjectUserSid	user	50

Intermediate Findings

Message	Entity Field	Entity Type	Risk Score
A default group policy object was modified on $Computer$ by $SubjectUserSid$	Computer	system	50

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: 13