[REQ-DC-126] Configure User Rights: Lock pages in memory on Domain Controllers

Target Scope

  • Applicable Systems: Domain Controllers (Tier 0 Active Directory infrastructure). (For Tier 0 Privileged Access Workstations, refer to tightened baseline REQ-PAW-106). (For Tier 2 Client Workstations and Member Servers, refer to standard baseline REQ-END-114).
  • Operating Systems: Windows Server 2016, Windows Server 2019, Windows Server 2022, and Windows Server 2025.

Implementation Details

  • Priority: Medium
  • GPO Path / Registry Location:
    • Policy Display Name: Lock pages in memory
    • Privilege Constant: SeLockMemoryPrivilege
    • GPO Path: Computer Configuration\Policies\Windows Settings\Security Settings\Local Policies\User Rights Assignment\Lock pages in memory
    • Registry Location: Stored inside local security database under privilege SeLockMemoryPrivilege set to No one (Empty).

Rationale

The SeLockMemoryPrivilege allows a process to lock physical memory pages in RAM using APIs such as VirtualLock and Address Windowing Extensions (AWE) via AllocateUserPhysicalPages. Locking pages prevents the Windows virtual memory manager from paging data out to disk in pagefile.sys, ensuring high-performance memory retention.

1. Technical Threat Vector & Abuse Mechanics

If granted to untrusted users or processes, SeLockMemoryPrivilege enables significant denial-of-service and kernel degradation attacks: (1) Memory Starvation: A malicious program can lock large swathes of physical RAM, preventing the OS memory manager from trimming working sets or servicing other processes. This leads to severe thrashing, unresponsiveness, and kernel exhaustion; (2) Security Telemetry Blind Spots: An attacker can pin memory structures containing malware artifacts, complicating memory forensics and page-table inspection.

2. Architectural Defense & Least Privilege Enforcement

Domain Controllers are the root of trust for the entire Active Directory forest, storing the directory database (ntds.dit), Kerberos master keys (krbtgt), and password hashes for all enterprise identities. Unrestricted allocation of user rights on Domain Controllers introduces devastating forest-compromise risks. Enforcing strict assignment of this privilege ensures that directory synchronization, authentication packages, and system execution remain strictly bounded to authorized directory components and Domain Administrators.

Under standard security baselines, SeLockMemoryPrivilege must be set to No one (Empty). Neither interactive users nor standard system accounts should possess this right on general workstations, PAWs, or Domain Controllers. Specialized database engines (such as Microsoft SQL Server) that utilize AWE memory locking should be configured with dedicated service accounts granted this privilege explicitly only on dedicated database servers.

3. MITRE ATT&CK Mapping

  • T1499 - Endpoint Denial of Service
  • T1055 - Process Injection

Legacy Impact & Compatibility

  • Operational Impact: Configuring SeLockMemoryPrivilege to No one has zero impact on desktop endpoints, PAWs, or Domain Controllers. Enterprise database hosts requiring Large Page allocations should receive tailored GPO exceptions on their dedicated Organizational Unit. Auditing is captured under Security Event ID 4704.

Implementation Steps

Option A: Group Policy Object (GPO) Configuration (Preferred)

  1. Open the Group Policy Management Console (gpmc.msc).
  2. Navigate to the targeted GPO linked to Tier 0 Domain Controller systems (e.g., Default Domain Controllers Policy).
  3. In the console tree, browse to: Computer Configuration\Policies\Windows Settings\Security Settings\Local Policies\User Rights Assignment
  4. Open the policy Lock pages in memory.
  5. Select the Define these policy settings check box.
  6. Click Add User or Group... and ensure the principal list is empty (or remove all assigned accounts/groups so that no principals are configured).
  7. Click Apply and OK.
  8. Apply and verify policy enforcement across target hosts using gpupdate /force and inspect with secedit /export /cfg C:\Windows\Temp\sec_audit.cfg.

Option B: PowerShell & Registry Configuration (Remediation / Non-GPO)

Download Script: Configure-DcUraSeLockMemoryPrivilege.ps1

# Configure-DcUraSeLockMemoryPrivilege.ps1
# Configure-DcUraSeLockMemoryPrivilege.ps1
$SecTempDir = Join-Path $env:TEMP "SecurityTemplates"
if (-not (Test-Path $SecTempDir)) { New-Item -Path $SecTempDir -ItemType Directory -Force | Out-Null }
$CfgFile = Join-Path $SecTempDir "ura_selockmemoryprivilege.cfg"
$DbFile = Join-Path $SecTempDir "secedit_selockmemoryprivilege.sdb"
$LogFile = Join-Path $SecTempDir "secedit.log"

$Process = Start-Process secedit -ArgumentList "/export /cfg `"$CfgFile`"" -Wait -NoNewWindow -PassThru
if ($Process.ExitCode -ne 0) { Throw "Failed to export security template" }

$ConfigText = Get-Content -Path $CfgFile -Raw
if ($ConfigText -notmatch "\[Privilege Rights\]") {
    $ConfigText += "`r`n[Privilege Rights]`r`n"
}

$Lines = $ConfigText -split "`r?`n"
$NewLines = @()
$InPriv = $false
$KeyAdded = $false

foreach ($Line in $Lines) {
    if ($Line -match "^\[(.*)\]$") {
        if ($Matches[1] -eq "Privilege Rights") {
            $InPriv = $true
        } else {
            $InPriv = $false
        }
    }
    if ($InPriv -and $Line -match "^\s*SeLockMemoryPrivilege\s*=") {
        $NewLines += "SeLockMemoryPrivilege = "
        $KeyAdded = $true
    } else {
        $NewLines += $Line
    }
}

if (-not $KeyAdded) {
    # Find Privilege Rights section index and insert it right after
    $Idx = $NewLines.IndexOf("[Privilege Rights]")
    if ($Idx -ge 0) {
        $NewLines.Insert($Idx + 1, "SeLockMemoryPrivilege = ")
    } else {
        $NewLines += "SeLockMemoryPrivilege = "
    }
}

$NewLines | Set-Content -Path $CfgFile -Force
$Proc = Start-Process secedit -ArgumentList "/configure /db `"$DbFile`" /cfg `"$CfgFile`" /areas USER_RIGHTS /log `"$LogFile`"" -Wait -NoNewWindow -PassThru
if ($Proc.ExitCode -ne 0) { Throw "Failed to configure secedit user rights" }
Remove-Item -Path $CfgFile, $DbFile -ErrorAction SilentlyContinue

To audit the hardening status: Download Script: Get-DcUraSeLockMemoryPrivilegeStatus.ps1

# Get-DcUraSeLockMemoryPrivilegeStatus.ps1
# Get-DcUraSeLockMemoryPrivilegeStatus.ps1
$SecTempDir = Join-Path $env:TEMP "SecurityTemplates"
if (-not (Test-Path $SecTempDir)) { New-Item -Path $SecTempDir -ItemType Directory -Force | Out-Null }
$CfgFile = Join-Path $SecTempDir "ura_audit_selockmemoryprivilege.cfg"

$Process = Start-Process secedit -ArgumentList "/export /cfg `"$CfgFile`"" -Wait -NoNewWindow -PassThru
if ($Process.ExitCode -ne 0) {
    Write-Output "Non-Compliant"
    exit 1
}

$ConfigText = Get-Content -Path $CfgFile -Raw
Remove-Item -Path $CfgFile -ErrorAction SilentlyContinue

$Match = $ConfigText -match "(?mi)^\s*SeLockMemoryPrivilege\s*=\s*(.*)$"
$CurrentValue = ""
if ($Match) {
    $CurrentValue = $Matches[1].Trim()
}

$Expected = ""
if ($CurrentValue -eq $Expected) {
    Write-Output "Compliant"
    exit 0
} else {
    Write-Output "Non-Compliant"
    exit 1
}

Sources & Compliance References

  • ANSSI Active Directory Hardening Guide: ANSSI Active Directory Hardening Guide: R28 (User Rights Assignment)
  • CIS Benchmark: 2.2.28 (L1) Ensure 'Lock pages in memory' is set to 'No One'
  • Microsoft Security Baseline: User Rights Configuration specifications
  • Microsoft Learn: User Rights Assignment Reference

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