Ensure 'Specify threat alert levels at which default action should not be taken when detected' is set to 'Enabled: Severe: 2 or 3'

MediumLevel 1Automateddefender

Description

This policy setting configures which automatic remediation action Microsoft Defender Antivirus will take for each threat alert level detection. Valid threat alert levels are: - 1 = Low - 2 = Medium - 4 = High - 5 = Severe Valid remediation action values are: - 2 = Quarantine - 3 = Remove - 6 = Ignore Threat alert levels are added under "options" for this setting. Each entry must be listed as a name value pair. Rationale: By default, Defender uses the action embedded in each threat’s malware signature (clean, quarantine, remove, etc.). Configuring this setting ensures the same action is always taken, regardless of how Microsoft classifies a specific threat. Audit reads the Group Policy registry value and prints 'compliant', 'unset' (policy not configured, reported as FAIL) or the non-compliant value. Registry value: HKLM\SOFTWARE\Policies\Microsoft\Windows Defender\Threats\ThreatSeverityDefaultAction:5 (REG_SZ); compliant when it is 2 or 3. Remediation writes 2 locally; in a domain set it through the ADMX so Group Policy does not revert it.

How it is checked

Audit method: Windows registry

registry

$v = (Get-ItemProperty -Path 'Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender\Threats\ThreatSeverityDefaultAction' -Name '5' -ErrorAction SilentlyContinue).'5'; if ($null -eq $v) { 'unset' } elseif (($null -ne $v -and @('2','3') -contains "$v")) { 'compliant' } else { "non-compliant: $v" }

Expected output: compliant

How it is fixed

Fix method: Shell command

shell

$p = 'Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender\Threats\ThreatSeverityDefaultAction'; if (-not (Test-Path -Path $p)) { New-Item -Path $p -Force | Out-Null }; New-ItemProperty -Path $p -Name '5' -Value '2' -PropertyType String -Force | Out-Null

Properties

Operating systems: Any
Tags: defenderantiviruscis-l1
Reference: CIS Microsoft Defender Antivirus Benchmark v1.0.0 - 1.15.4 Ensure 'Specify threat alert levels at which default action should not be taken when detected' is set to 'Enabled: Severe: 2 or 3'

Check this host

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

shell

tmaegis scan --target defender