[REQ-PAW-063] Enable File Hash Computation for PAWs

Target Scope

• Applicable Systems: Privileged Access Workstations (PAWs) used for Tier 0 directory administration.
• Operating Systems: Windows 10 Enterprise (1607+) and Windows 11 Enterprise.

Implementation Details

• Priority: Medium
• GPO Path / Registry Location:
  • GPO Path: Computer Configuration\Administrative Templates\Windows Components\Windows Defender Antivirus\MpEngine
  • Registry Location:
    • HKLM\SOFTWARE\Policies\Microsoft\Windows Defender\MpEngine
      • EnableFileHashComputation = 1 (REG_DWORD)

Rationale

Computing cryptographic file hashes allows Defender to pass hashes of scanned files to cloud and SIEM PAW platforms. This enables precise IOC matches, file tracking, and correlation with threat intelligence repositories.

Legacy Impact & Compatibility

Minor CPU/Disk I/O impact when scanning large directories.

Implementation Steps

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

1. Navigate to: Computer Configuration\Administrative Templates\Windows Components\Windows Defender Antivirus\MpEngine
2. Set 'Enable file hash computation feature' to 'Enabled'

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

Download Script: Configure-PawDefenderFileHash.ps1

# Configure-PawDefenderFileHash.ps1
Set-MpPreference -EnableFileHashComputation $true
$MpEnginePath = "HKLM:\SOFTWARE\Policies\Microsoft\Windows Defender\MpEngine"
if (-not (Test-Path $MpEnginePath)) { New-Item -Path $MpEnginePath -Force | Out-Null }
Set-ItemProperty -Path $MpEnginePath -Name "EnableFileHashComputation" -Value 1 -Type DWord -Force

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

# Get-PawDefenderFileHashStatus.ps1
$Pref = Get-MpPreference
$Reg = Get-ItemProperty -Path "HKLM:\SOFTWARE\Policies\Microsoft\Windows Defender\MpEngine" -Name "EnableFileHashComputation" -ErrorAction SilentlyContinue
if ($Pref.EnableFileHashComputation -eq $true -or ($Reg -and $Reg.EnableFileHashComputation -eq 1)) {
    Write-Output "Compliant"
    exit 0
} else {
    Write-Output "Non-Compliant"
    exit 1
}

Sources & Compliance References

• CIS Microsoft Windows 10 Benchmark: Section 18.9 (Windows Defender Antivirus configuration parameters)
• ANSSI Active Directory Hardening Guide: Protective controls baselines on Privileged Access Workstations