Ensure 'ASR: Block abuse of exploited vulnerable signed drivers' is set to 'Block'

MediumLevel 1Automatedintune-defender

Description

This rule prevents an application from writing a vulnerable signed driver to disk. The recommended state for this setting is: Block. Note: The Block abuse of exploited vulnerable signed drivers setting does not block a driver that already exists on the system from being loaded. Audit: reads the Intune PolicyManager ASR rules value (via the WinningProvider GUID) and requires the rule entry 56a863a9-875e-4185-98a7-b882c64b5ce5=1 (Block).

How it is checked

Audit method: Windows registry

registry

$p = (Get-ItemProperty -Path 'Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\PolicyManager\current\device\Defender' -Name 'AttackSurfaceReductionRules_WinningProvider' -ErrorAction SilentlyContinue).'AttackSurfaceReductionRules_WinningProvider'; if (-not $p) { 'non-compliant: no ASR WinningProvider' } else { $p = ([string]$p).Trim('{}'); $k = 'Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\PolicyManager\Providers\' + $p + '\default\Device\Defender'; if (-not (Test-Path $k)) { $k = 'Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\PolicyManager\Providers\{' + $p + '}\default\Device\Defender' }; $v = (Get-ItemProperty -Path $k -Name 'AttackSurfaceReductionRules' -ErrorAction SilentlyContinue).'AttackSurfaceReductionRules'; $have = @(([string]$v) -split '\|' | ForEach-Object { $_.Trim().ToLower() }); $want = @('56a863a9-875e-4185-98a7-b882c64b5ce5=1'); if (@($want | Where-Object { $have -contains $_ }).Count -gt 0) { 'compliant' } else { 'non-compliant: ' + $v } }

Expected output: compliant

How it is fixed

Fix method: Guidance or infrastructure patch

To establish the recommended configuration via configuration profiles, set the following Settings Catalog path to Block. Defender\Block abuse of exploited vulnerable signed drivers (Device)

Properties

Operating systems: Any
Tags: intune-defenderintuneregistry
Reference: CIS Microsoft Intune for Microsoft Defender Antivirus Benchmark v1.0.0 - 2.10 Ensure 'ASR: Block abuse of exploited vulnerable signed drivers' is set to 'Block'

Check this host

Run this on a machine you are allowed to audit. The scan is read-only.

shell

tmaegis scan --target intune-defender