GPLINK

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Summary


Forestall ACL Alias	GPLINK
Affected Object Types	Organizational Unit
Exploitation Certainty	Certain

Description

The GPLINK edge in Active Directory indicates that a Group Policy Object (GPO) is linked to an Organizational Unit (OU), domain, or site. It serves as a reference that helps visualize where specific GPOs are applied within the directory structure.

Accurately mapping these links is essential for understanding the scope and impact of Group Policy across the environment. By analyzing GPLINK relationships, administrators and security professionals can identify which policies are in effect for particular groups of users or computers, ensure proper policy inheritance, and detect potentially misconfigured or overly permissive links that could introduce security risks or configuration drift.

Identification

PowerShell

Active Directory Module

Using the ActiveDirectory PowerShell module, you can enumerate GPLINK entries.

1. Find-GPLINK function

function Find-GPLINK {
    [CmdletBinding()]
    param (
        [string]$Target,                     # Optional OU name
        [string]$OutputPath = "GPLINK.csv"   # CSV output file path
    )
    $OUs = Get-ADOrganizationalUnit -Filter * -Properties gPLink |
        Select-Object Name, gPLink
    if ($Target) {
        $OUs = $OUs | Where-Object { $_.Name -eq $Target }
    }
    $OUs | Export-Csv -Path $OutputPath -NoTypeInformation -Encoding UTF8
    return $OUs
}

2. Scan all OUs in the domain

Find-GPLINK

3. Scan a specific OU

Find-GPLINK -Target Workstations

.NET Directory Services

By leveraging PowerShell’s built-in .NET DirectoryServices namespace, you can enumerate GenericWGPLINKrite entries without relying on any external modules or dependencies.

1. Find-GPLINKSimple function

function Find-GPLINKSimple {
    [CmdletBinding()]
    param ([string]$Target,[string]$OutputPath = "GPLINK.csv")
    if ($Target) {
        try {
            $entries = @( New-Object System.DirectoryServices.DirectoryEntry("LDAP://$Target") )
        }
        catch {Write-Error "Failed to bind to '$Target': $_";return}
    }
    else {
        try {
            $root      = New-Object System.DirectoryServices.DirectoryEntry("LDAP://RootDSE")
            $baseDN    = $root.Properties["defaultNamingContext"].Value
            $ldapPath  = "LDAP://$baseDN"
            $searchRoot= New-Object System.DirectoryServices.DirectoryEntry($ldapPath)
            $searcher = New-Object System.DirectoryServices.DirectorySearcher($searchRoot)
            $searcher.Filter   = "(objectCategory=organizationalUnit)"
            $searcher.PageSize = 1000
            [void]$searcher.PropertiesToLoad.Add("name")
            [void]$searcher.PropertiesToLoad.Add("gPLink")
            $hits = $searcher.FindAll()
        }
        catch {
            Write-Error "LDAP search failed: $_";return
        }
        $entries = foreach ($hit in $hits) {
            try { $hit.GetDirectoryEntry() } catch { Write-Warning "Failed to bind entry: $_"; continue }
        }
    }
    $results = foreach ($entry in $entries) {
        [PSCustomObject]@{
            Name   = $entry.Properties["name"][0]
            gPLink = $entry.Properties["gPLink"][0]}}
    $results | Export-Csv -Path $OutputPath -NoTypeInformation -Encoding UTF8
    return $results
}

2. Scan all OUs in the domain

Find-GPLINKSimple

3. Scan a specific OU

Find-GPLINKSimple -Target "OU=Workstations,DC=Forestall,DC=labs"

Group Policy Management

1. Open Group Policy Management.

2. Expand the OU name.

Exploitation

This edge shows linkage only. Compromise impact comes from who controls the GPO or who can manage links on the OU (e.g., GPLink, GPOptions). See ManageGPLink.

If control over a GPO is obtained, it means that all objects linked to that GPO will be affected by its settings. See GPOWrite.

Mitigation

To mitigate GPLINK using Group Policy Management, follow the steps below:

1. Open Group Policy Management.

2. Expend or click to the OU name.

3. Right-click the Group Policy.

4. Right-click the linked GPO under the OU and choose Delete to remove the link (this does not delete the GPO itself).

Detection

Adding new Access Control Entries to Active Directory objects changes the ntSecurityDescriptor attribute of the objects themselves. These changes can be detected with the 5136 and 4662 Event IDs to identify potentially dangerous modifications.

Event ID	Description	Fields/Attributes	References
5136	A directory service object was modified.	AttributeLDAPDisplayName: gPLink, ObjectDN (the OU), New/Old Value	https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-5136
4662	An operation was performed on an object.	AccessMask / Properties indicating write to gPLink	https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4662