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

MediumLevel 1Automateddefender

Description

This policy setting configures which automatic remediation action Microsoft Defender Antivirus will take for each threat alert level detection. The recommended state for this setting is: Enabled. 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:Threats_ThreatSeverityDefaultAction (REG_DWORD); compliant when it is 1. Remediation writes 1 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

$v = (Get-ItemProperty -Path 'Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender\Threats' -Name 'Threats_ThreatSeverityDefaultAction' -ErrorAction SilentlyContinue).'Threats_ThreatSeverityDefaultAction'; if ($null -eq $v) { 'unset' } elseif (($null -ne $v -and @(1) -contains [int64]$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'; if (-not (Test-Path -Path $p)) { New-Item -Path $p -Force | Out-Null }; New-ItemProperty -Path $p -Name 'Threats_ThreatSeverityDefaultAction' -Value 1 -PropertyType DWord -Force | Out-Null

Properties

Operating systems: Any
Tags: defenderantiviruscis-l1
Reference: CIS Microsoft Defender Antivirus Benchmark v1.0.0 - 1.15.1 Ensure 'Specify threat alert levels at which default action should not be taken when detected' is set to 'Enabled'

Check this host

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

shell

tmaegis scan --target defender