SV-220841r991589: Users must not be allowed to ignore Windows Defender SmartScreen filter warnings for unverified files in Microsoft Edge. | Microsoft Windows 10 STIG SCAP Benchmark

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Assessment Title

Rule Text

Users must not be allowed to ignore Windows Defender SmartScreen filter warnings for unverified files in Microsoft Edge.

Description

Discussion Text

The Windows Defender SmartScreen filter in Microsoft Edge provides warning messages and blocks potentially malicious websites and file downloads. If users are allowed to ignore warnings from the Windows Defender SmartScreen filter they could still download potentially malicious files.

How this relates to the STIG checklist: STIG vs SCAP benchmark.

IA Controls

NIST SP 800-53

Not mappedCCI-000366SV-78191V-63701

References

DPMS Target Microsoft Windows 10 DISA DPMS Target Microsoft Windows 10 4072

SCC Automation Reference

The reconstructed evaluation script behind this rule's OVAL check(s) — every module a compound check combines, with this rule's own concrete values and DISA's SCC tool's real per-module mechanism curated from static teardown of SCC releases.

# Windows PowerShell
# Reconstructed from oval:mil.disa.stig.windows10:def:220841
# Users must not be allowed to ignore Windows Defender SmartScreen filter warnings for unverified files in Microsoft Edge.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# PreventOverrideAppRepUnknown registry value is set to 1
# registry_object (registry_test)
function test_1 {
  return (((@{String='reg_sz';ExpandString='reg_expand_sz';Binary='reg_binary';DWord='reg_dword';MultiString='reg_multi_sz';QWord='reg_qword';None='reg_none'}[(Get-Item -Path 'Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\MicrosoftEdge\PhishingFilter').GetValueKind('PreventOverrideAppRepUnknown').ToString()]) -eq 'reg_dword') -and (((Get-ItemProperty -Path 'Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\MicrosoftEdge\PhishingFilter' -Name 'PreventOverrideAppRepUnknown' -ErrorAction SilentlyContinue) | Select-Object -ExpandProperty 'PreventOverrideAppRepUnknown') -eq 1))
}

if (test_1) {
  Write-Output "PASS"
} else {
  Write-Output "FAIL"
}

Assessment Script Powered by AISyntax-verified

A standalone PowerShell script to assess this control automatically. Review before running it in your environment.

Syntax-checked as valid PowerShell. Not executed here — running it for real needs the actual ms_windows_10 target this check assesses.

# OVAL Definition: oval:mil.disa.stig.windows10:def:220841
if (!(Test-Path -Path "HKLM:\SOFTWARE\Policies\Microsoft\MicrosoftEdge\PhishingFilter\PreventOverrideAppRepUnknown") -or ((Get-ItemProperty -Path "HKLM:\SOFTWARE\Policies\Microsoft\MicrosoftEdge\PhishingFilter\PreventOverrideAppRepUnknown").PreventOverrideAppRepUnknown -ne 1)) {exit 1} else {exit 0}

Remediation

Configure the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Edge >> "Prevent bypassing Windows Defender SmartScreen prompts for files" to "Enabled". 

Windows 10 includes duplicate policies for this setting. It can also be configured under Computer Configuration >> Administrative Templates >> Windows Components >> Windows Defender SmartScreen >> Microsoft Edge.