PowerPoint: Block Editing If File Validation Fails

πŸ’Ό Management Samenvatting

Block editing if PowerPoint file validation fails - prevents interaction with corrupted/malicious files (exploit prevention).

Aanbeveling
IMPLEMENT
Risico zonder
High
Risk Score
7/10
Implementatie
2u (tech: 1u)
Van toepassing op:
βœ“ Microsoft PowerPoint

File validation failure = corruption/malware indicator: File validation: PowerPoint checks file structure integrity (header, format compliance), Failure reasons: Corrupted file (disk errors, incomplete downloads), Maliciously crafted file (exploit embedded - buffer overflow, memory corruption). Block editing: Failed validation β†’ file MIGHT contain exploit β†’ editing triggers exploit β†’ code execution. Defense: Block editing β†’ user can view (Protected View) maar CANNOT edit β†’ exploit not triggered.

PowerShell Modules Vereist
Primary API: Intune / GPO
Connection: Registry-based
Required Modules:

Implementatie

Block editing on failure: Policy: Set document behavior if file validation fails: Block files, Effect: Validation fails β†’ Protected View (read-only), User cannot edit (no enable button), Safe workflow: View file β†’ if legitimate β†’ re-save from original source.

Vereisten

  1. PowerPoint 2016+
  2. File validation enabled (prerequisite)
  3. Intune of GPO

Implementatie

Intune Settings Catalog: PowerPoint\Security\Trust Center\File Validation β†’ Set document behavior if file validation fails: Block files (read-only Protected View).

Compliance

CIS Office Benchmark L1, BIO 12.02, ISO 27001 A.12.2.1.

Monitoring

Gebruik PowerShell-script file-validation-fails-no-edit.ps1 (functie Invoke-Monitoring) – Controleren.

Remediatie

Gebruik PowerShell-script file-validation-fails-no-edit.ps1 (functie Invoke-Remediation) – Herstellen.

Compliance & Frameworks

Automation

Gebruik het onderstaande PowerShell script om deze security control te monitoren en te implementeren. Het script bevat functies voor zowel monitoring (-Monitoring) als remediation (-Remediation).

PowerShell
<# .SYNOPSIS Voorkomt bewerking van bestanden die bestandsvalidatie niet doorstaan in PowerPoint .DESCRIPTION Dit script implementeert CIS control O365-PT-000012 voor het voorkomen van bewerking van bestanden die bestandsvalidatie niet doorstaan in Microsoft PowerPoint. Dit beschermt tegen potentieel schadelijke bestanden die de validatie niet hebben gehaald. .REQUIREMENTS - PowerShell 5.1 of hoger - Lokale administrator rechten voor registry wijzigingen - Microsoft PowerPoint geΓ―nstalleerd .PARAMETER Monitoring Controleert de huidige compliance status .PARAMETER Remediation Past de aanbevolen configuratie toe .PARAMETER Revert Herstelt de originele configuratie .PARAMETER WhatIf Toont wat er zou gebeuren zonder wijzigingen door te voeren .EXAMPLE .\file-validation-fails-no-edit.ps1 -Monitoring Controleert of bewerking is geblokkeerd voor niet-gevalideerde bestanden .EXAMPLE .\file-validation-fails-no-edit.ps1 -Remediation Blokkeert bewerking van niet-gevalideerde bestanden .NOTES Registry pad: HKCU:\Software\Policies\Microsoft\Office\16.0\POWERPOINT\Security Waarde: filevalidationfailsnoedit = 1 CIS Control: O365-PT-000012 DISA STIG: Microsoft Office 365 ProPlus v3r3 #> #Requires -Version 5.1 param( [switch]$Monitoring, [switch]$Remediation, [switch]$Revert, [switch]$WhatIf ) # Globale variabelen $RegistryPath = "HKCU:\Software\Policies\Microsoft\Office\16.0\POWERPOINT\Security" $ValueName = "filevalidationfailsnoedit" $ExpectedValue = 1 $ControlID = "O365-PT-000012" function Test-Compliance { try { if (-not (Test-Path $RegistryPath)) { return $false } $currentValue = Get-ItemProperty -Path $RegistryPath -Name $ValueName -ErrorAction SilentlyContinue return ($currentValue -and $currentValue.$ValueName -eq $ExpectedValue) } catch { return $false } } function Invoke-Monitoring { Write-Host "Monitoring ${ControlID}: Bewerking blokkeren voor niet-gevalideerde bestanden" -ForegroundColor Green try { if (-not (Test-Path $RegistryPath)) { Write-Host "βœ— Registry pad bestaat niet: $RegistryPath" -ForegroundColor Red return $false } $currentValue = Get-ItemProperty -Path $RegistryPath -Name $ValueName -ErrorAction SilentlyContinue if ($currentValue -and $currentValue.$ValueName -eq $ExpectedValue) { Write-Host "βœ“ Control compliant: ${ValueName} = $ExpectedValue" -ForegroundColor Green return $true } else { $actualValue = if ($currentValue) { $currentValue.$ValueName } else { "Not Set" } Write-Host "βœ— Control non-compliant: ${ValueName} = $actualValue (Expected: $ExpectedValue)" -ForegroundColor Red return $false } } catch { Write-Host "βœ— Fout bij controleren registry instelling: $($_.Exception.Message)" -ForegroundColor Red return $false } } function Invoke-Remediation { Write-Host "Remediating ${ControlID}: Bewerking blokkeren voor niet-gevalideerde bestanden" -ForegroundColor Yellow try { if ($WhatIf) { Write-Host "WhatIf: Zou registry waarde instellen: ${ValueName} = $ExpectedValue" -ForegroundColor Cyan return $true } if (-not (Test-Path $RegistryPath)) { Write-Host "Registry pad aanmaken: $RegistryPath" -ForegroundColor Yellow New-Item -Path $RegistryPath -Force | Out-Null } Set-ItemProperty -Path $RegistryPath -Name $ValueName -Value $ExpectedValue -Type DWord -Force Write-Host "βœ“ Registry waarde succesvol ingesteld: ${ValueName} = $ExpectedValue" -ForegroundColor Green Start-Sleep -Seconds 1 return Invoke-Monitoring } catch { Write-Host "βœ— Fout bij configureren registry instelling: $($_.Exception.Message)" -ForegroundColor Red return $false } } function Invoke-Revert { Write-Host "Reverting ${ControlID}: Bestandsvalidatie bewerking instelling herstellen" -ForegroundColor Yellow try { if ($WhatIf) { Write-Host "WhatIf: Zou registry waarde verwijderen: ${ValueName}" -ForegroundColor Cyan return $true } if (Test-Path $RegistryPath) { Remove-ItemProperty -Path $RegistryPath -Name $ValueName -ErrorAction SilentlyContinue Write-Host "βœ“ Registry waarde verwijderd: ${ValueName}" -ForegroundColor Green } return $true } catch { Write-Host "βœ— Fout bij herstellen registry instelling: $($_.Exception.Message)" -ForegroundColor Red return $false } } # Hoofd uitvoering try { if ($Monitoring) { $result = Invoke-Monitoring exit $(if ($result) { 0 } else { 1 }) } elseif ($Remediation) { $result = Invoke-Remediation exit $(if ($result) { 0 } else { 1 }) } elseif ($Revert) { $result = Invoke-Revert exit $(if ($result) { 0 } else { 1 }) } else { Write-Host "Gebruik: .\file-validation-fails-no-edit.ps1 [-Monitoring] [-Remediation] [-Revert] [-WhatIf]" -ForegroundColor Yellow Write-Host " -Monitoring: Controleer huidige compliance status" -ForegroundColor White Write-Host " -Remediation: Pas aanbevolen configuratie toe" -ForegroundColor White Write-Host " -Revert: Herstel originele configuratie" -ForegroundColor White Write-Host " -WhatIf: Toon wat er zou gebeuren" -ForegroundColor White } } catch { Write-Host "βœ— Onverwachte fout: $($_.Exception.Message)" -ForegroundColor Red exit 1 }

Risico zonder implementatie

Risico zonder implementatie
High: Hoog: Failed validation + editing = exploit triggers (code execution).

Management Samenvatting

PowerPoint: Block editing if file validation fails. Exploit prevention. Protected View only. Implementatie: 1-2 uur.