GPOWrite

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Summary


Forestall ACL Alias	GPOWrite
AD Alias	GpoEdit
Affected Object Types	Group Policies
Exploitation Certainty	Certain

Description

The GPOWrite permission in Active Directory grants a user GpoEdit access, enabling them to modify and manage Group Policy Objects directly. When properly assigned, this permission allows authorized administrators to create, configure, and update policies that control user environments and system behaviors across the domain. With GPOWrite, administrators can define security settings, deploy software, configure system preferences, and implement organizational policies in a centralized manner.

However, if granted inappropriately, the GPOWrite permission poses significant security risks. An attacker or unauthorized user with GPOWrite access could alter critical security settings, disable protective measures, or implement harmful configurations affecting all linked computers and users. Since Group Policy settings often apply to entire organizational units or domains, this permission effectively enables wide-reaching changes across the network environment. Additionally, attackers could embed malicious commands or code in these configurations. Since such scripts may run with elevated privileges (e.g., Domain Admins), any harmful modifications can rapidly compromise the network.

Identification

PowerShell

Active Directory Module

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

1. Find-GPOWrite function

function Find-GPOWrite {
    [CmdletBinding()]
    param([string]$Target = $null,[string]$OutputPath = "GPOWrite.csv",[switch]$ExcludeAdmins = $false)
    Import-Module ActiveDirectory -ErrorAction Stop
    Import-Module GroupPolicy -ErrorAction Stop
    Write-Host "Gathering Group Policy Objects and inspecting AD ACLs for explicit write access..."
    # Build exclusion SID list if requested
    $ExcludedSIDStrings = @()
    if ($ExcludeAdmins) {
        Write-Host "Excluding default administrative groups and built-in accounts."
        try {
            $ExcludedSIDStrings += (New-Object System.Security.Principal.NTAccount "NT AUTHORITY\SYSTEM").Translate([System.Security.Principal.SecurityIdentifier]).Value
            $ExcludedSIDStrings += (New-Object System.Security.Principal.NTAccount "SYSTEM").Translate([System.Security.Principal.SecurityIdentifier]).Value
            $ExcludedSIDStrings += (New-Object System.Security.Principal.NTAccount "NT AUTHORITY\ENTERPRISE DOMAIN CONTROLLERS").Translate([System.Security.Principal.SecurityIdentifier]).Value
        } catch {}
        # Creator Owner SID
        $ExcludedSIDStrings += [System.Security.Principal.SecurityIdentifier]::new("S-1-3-0").Value
        foreach ($grp in @(
            "Domain Admins","Enterprise Admins","Schema Admins","Cert Publishers",
            "Group Policy Creator Owners","Domain Controllers","Key Admins",
            "Enterprise Key Admins","DnsAdmins","RAS and IAS Servers"
        )) {
            try { $ExcludedSIDStrings += (Get-ADGroup -Identity $grp -ErrorAction Stop).SID.Value } catch {}
        }
    }
    $results   = @()
    $gposToScan = @()
    try {
        if ($Target) {
            Write-Verbose "Target specified. Looking for GPO: '$Target'."
            $gpoToScan = Get-GPO -Name $Target -ErrorAction Stop
            if ($gpoToScan) {
                $gposToScan += $gpoToScan
                Write-Host "Inspecting explicit write permissions on GPO: '$Target'."
            } else {
                Write-Output "GPO '$Target' not found."
                return
            }
        } else {
            Write-Verbose "No target specified. Getting all GPOs."
            $gposToScan = Get-GPO -All -ErrorAction Stop
            Write-Host "Inspecting explicit write permissions on all GPOs in the domain."
        }
        if (-not $gposToScan) {
            Write-Output "No Group Policy Objects found matching the criteria."
            return
        }
        $domainDN = (Get-ADDomain).DistinguishedName
        # Define which AD rights count as "write-like"
        $ADR = [System.DirectoryServices.ActiveDirectoryRights]
        $writeRightsList = @($ADR::WriteProperty,$ADR::GenericWrite,$ADR::WriteDacl,$ADR::WriteOwner)
        foreach ($gpo in $gposToScan) {
            Write-Verbose "Inspecting GPO '$($gpo.DisplayName)' (ID: $($gpo.Id))."
            # AD object of the GPO (GPC)
            $gpoDN  = "CN={$($gpo.Id)},CN=Policies,CN=System,$domainDN"
            $adPath = "AD:$gpoDN"
            try {
                $acl  = Get-Acl -Path $adPath -ErrorAction Stop
                $aces = $acl.Access
                foreach ($ace in $aces) {
                    # Only consider Allow, non-inherited ACEs
                    if ($ace.AccessControlType -ne [System.Security.AccessControl.AccessControlType]::Allow) { continue }
                    if ($ace.IsInherited) { continue }
                    # Exclusion filter (by SID)
                    $trusteeSidString = $null
                    try {
                        $trusteeSidString = $ace.IdentityReference.Translate([System.Security.Principal.SecurityIdentifier]).Value
                    } catch {
                        $trusteeSidString = "S-1-0-0" # Null SID fallback if translation fails
                    }
                    if ($ExcludeAdmins -and ($ExcludedSIDStrings -contains $trusteeSidString)) {
                        Write-Verbose "Trustee '$($ace.IdentityReference.Value)' is excluded. Skipping."
                        continue
                    }
                    # Check if ACE has any of the write-like rights
                    $matchedRights = @()
                    foreach ($wr in $writeRightsList) {
                        if (($ace.ActiveDirectoryRights -band $wr) -eq $wr) {
                            $matchedRights += $wr.ToString()
                        }
                    }
                    if ($matchedRights.Count -gt 0) {
                        # Record result; keep same CSV columns as your previous function
                        $results += [PSCustomObject]@{
                            GPOName    = $gpo.DisplayName
                            GPOId      = $gpo.Id
                            Trustee    = $ace.IdentityReference.Value
                            Permission = ($matchedRights -join ",")
                        }
                    }
                }
            }
            catch {
                Write-Warning "Error retrieving ACL for GPO '$($gpo.DisplayName)' (ID: $($gpo.Id)): $($_.Exception.Message)"
            }
        }
    }
    catch {
        Write-Error "Failed to retrieve Group Policy Objects: $($_.Exception.Message)"
        return
    }
    # Export the results to CSV if any were found
    if ($results.Count -gt 0) {
        $exclusionMessage = if ($ExcludeAdmins) { " (excluding default admin groups and built-in accounts)" } else { "" }
        Write-Host "Found $($results.Count) explicit write ACE(s) on GPO AD objects$exclusionMessage."
        try {
            $results |
                Sort-Object -Unique GPOName, GPOId, Trustee, Permission |
                Export-Csv -Path $OutputPath -NoTypeInformation -Encoding UTF8
            Write-Output "Results exported successfully to '$OutputPath'"
        }
        catch {
            Write-Error "Failed to export results to CSV file '$OutputPath': $($_.Exception.Message)"
        }
    } else {
        $exclusionMessage = if ($ExcludeAdmins) { " (excluding default admin groups and built-in accounts)" } else { "" }
        Write-Output "No explicit write ACEs found on GPO AD objects$exclusionMessage."
    }
}

2. Search all GPOs in the domain

Find-GPOWrite

3. To scan a specific GPO

Find-GPOWrite -Target "LAPSSetup"

4. To exclude default admin ACLs to improve visibility

Find-GPOWrite -ExcludeAdmins

.NET Directory Services

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

1. Find-GPOWriteSimple function

function Find-GPOWriteSimple {
    [CmdletBinding()]
    param ([string]$Target = $null,[string]$OutputPath   = "GPOWrite.csv",[switch]$ExcludeAdmins)
    $results = [System.Collections.Generic.List[PSObject]]::new()
    $domain  = $env:USERDOMAIN
    if ($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
            $gpoPath    = "LDAP://CN=Policies,CN=System,$baseDN"
            $searchRoot = New-Object System.DirectoryServices.DirectoryEntry($gpoPath)
            $searcher = [System.DirectoryServices.DirectorySearcher]::new($searchRoot)
            $searcher.Filter           = "(objectCategory=groupPolicyContainer)"
            $searcher.PageSize         = 1000
            [void]$searcher.PropertiesToLoad.Add("distinguishedName")
            [void]$searcher.PropertiesToLoad.Add("displayName")
            $hits = $searcher.FindAll()
        }
        catch {
            Write-Error "LDAP enumeration failed: $_"
            return
        }
        $entries = foreach ($hit in $hits) {
            try { $hit.GetDirectoryEntry() }
            catch { Write-Warning "Could not bind entry: $_"; continue }}
    }
    $ExcludedNames = @(
        'SYSTEM','NT AUTHORITY\SYSTEM','BUILTIN\Administrators','BUILTIN\Account Operators','BUILTIN\Backup Operators','BUILTIN\Print Operators','BUILTIN\Server Operators','BUILTIN\Replicator',
        'CREATOR OWNER',"$domain\Domain Admins","$domain\Enterprise Admins","$domain\Schema Admins","$domain\Cert Publishers","$domain\Group Policy Creator Owners","$domain\Domain Controllers","$domain\Key Admins",
        "$domain\Enterprise Key Admins","$domain\DnsAdmins", "$domain\RAS and IAS Servers")
    foreach ($entry in $entries) {
        try {
            $acl  = $entry.ObjectSecurity
            $aces = $acl.GetAccessRules($true, $true, [System.Security.Principal.SecurityIdentifier])
        }
        catch {
            Write-Warning "Could not read ACL for $($entry.distinguishedName): $_"
            continue
        }
        foreach ($ace in $aces) {
            if (
                $ace.AccessControlType -eq [System.Security.AccessControl.AccessControlType]::Allow -and
                ($ace.ActiveDirectoryRights -band [System.DirectoryServices.ActiveDirectoryRights]::WriteProperty) -and
                -not $ace.IsInherited
            ) {
                $principal = try { $ace.IdentityReference.Translate([System.Security.Principal.NTAccount]).Value} catch {$ace.IdentityReference.Value }
                if ($ExcludeAdmins -and $ExcludedNames -contains $principal) {
                    continue
                }
                $results.Add([PSCustomObject]@{
                    GPOName    = $entry.Properties["displayName"].Value
                    GPOId      = $entry.Properties["cn"].Value
                    Trustee    = $principal
                    Permission = 'WriteProperty'
                })
            }
        }
    }
    $unique = $results |
        Sort-Object GPOName, GPOId, Trustee -Unique
    if ($unique.Count -gt 0) {
        $unique |
          Export-Csv -Path $OutputPath -NoTypeInformation -Encoding UTF8
        Write-Host "Exported $($unique.Count) entr$(if ($unique.Count -eq 1){'y'}else{'ies'}) to $OutputPath"
    }
    else {
        Write-Host "No GPOs found with explicit write permissions."
    }
}

2. Search all GPOs in the domain

Find-GPOWriteSimple

3. To scan a specific GPO

Find-GPOWriteSimple -Target "CN={31B2F340-016D-11D2-945F-00C04FB984F9},CN=Policies,CN=System,DC=Forestall,DC=labs"

4. To exclude default admin ACLs to improve visibility

Find-GPOWriteSimple -ExcludeAdmins

Group Policy Management

1. Open Group Policy Management.

2. Find and click on the Group Policy.

3. Select Delegation from the context menu.

4. In the groups and users list, locate the relevant users and groups.

Exploitation

Windows

Using `Group Policy Management`.

A logon script runs automatically as part of a user’s sign-in sequence. To add or configure a logon script, follow these steps:

1. Open Group Policy Management.

2. Find and right-click on the Group Policy.

3. Select Edit... from the context menu.

4. Navigate to User Configuration > Policies > Windows Settings > Scripts (Logon/Logoff) in the Group Policy Management Editor.

5. Double-click Logon

6. Click Add…, then either browse to the script or type its full path.

7. Specify any required script parameters, then click OK.

8. Click Apply, then OK to save your changes and close the dialog boxes.

Important Note

If this logon/logoff script targets authorized users (e.g., the Default Domain Policy affects all authenticated users, including administrators), it will execute with high privileges during login or logout.

Using SharpGPOAbuse

Adding a Local Admin

SharpGPOAbuse.exe --AddLocalAdmin --UserAccount <user> --GPOName "<GPONAME>" --Force

Example:

SharpGPOAbuse.exe --AddLocalAdmin --UserAccount adam --GPOName "LAPSSETUP" --Force

Linux

Using pyGPOAbuse

Add the user John to the local administrators group (Password: H4x00r123..)

python3 pygpoabuse.py -gpo-id "<gpoid>" <domain>/<user>:'<pass>'

Example:

python3 pygpoabuse.py -gpo-id "327f18b4-eeef-49d6-8071-161fc5d69782" FORESTALL.LABS/adam:'Temp123!'

Granted by

This edge is available to any principal holding broader rights over the GPO object. GenericAll, GenericWrite, and Owner on a GPO all permit editing its settings.

Mitigation

Access Control Entries identified as dangerous should be removed by following the steps below.

1. Open Group Policy Management.

2. Find and click on the Group Policy.

3. Select Delegation from the context menu.

4. In the groups and users list, locate and remove the users and groups.

Detection

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

Event ID	Description	Fields/Attributes	References
5136	A directory service object was modified.	ntSecurityDescriptor	https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-5136\|
4662	An operation was performed on an object.	AccessList, AccessMask	https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4662\|

GPOWrite

Summary

Description

Identification

PowerShell

Active Directory Module

.NET Directory Services

Group Policy Management

Exploitation

Windows

Using Group Policy Management.

Important Note

Using SharpGPOAbuse

Linux

Granted by

Mitigation

Detection

References

Using `Group Policy Management`.