Microsoft Defender Antivirus
TMA-DEFENDER-1.6.1.15
Ensure 'Configure Attack Surface Reduction rules: Set the state for each ASR rule' is set to 'b2b3f03d-6a65-4f7b-a9c7- 1c7ef74a9ba4:1'
Description
With this rule, admins can prevent unsigned or untrusted executable files from running from USB removable drives, including SD cards. Blocked file types include executable files (such as .exe, .dll, or .scr). Rule ID and name: - b2b3f03d-6a65-4f7b-a9c7-1c7ef74a9ba4 (Block untrusted and unsigned processes that run from USB) The recommended state for this setting is: b2b3f03d-6a65-4f7b-a9c7- 1c7ef74a9ba4:1 (Block). Rationale: Attack surface reduction helps prevent actions and apps that are typically used by exploit-seeking malware to infect machines. 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\Windows Defender Exploit Guard\ASR\Rules:b2b3f03d-6a65-4f7b-a9c7-1c7ef74a9ba4 (REG_SZ); compliant when it is 1.
How it is checked
Audit method: Windows registry
$v = (Get-ItemProperty -Path 'Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender\Windows Defender Exploit Guard\ASR\Rules' -Name 'b2b3f03d-6a65-4f7b-a9c7-1c7ef74a9ba4' -ErrorAction SilentlyContinue).'b2b3f03d-6a65-4f7b-a9c7-1c7ef74a9ba4'; if ($null -eq $v) { 'unset' } elseif (($null -ne $v -and @('1') -contains "$v")) { 'compliant' } else { "non-compliant: $v" }- Expected output
compliant
How it is fixed
Fix method: Guidance or infrastructure patch
Configure through Group Policy: Computer Configuration\Policies\Administrative Templates\Windows Components\Microsoft Defender Antivirus\Microsoft Defender Exploit Guard\Attack Surface Reduction\Configure Attack Surface Reduction rules: Set the state for each ASR rule = b2b3f03d-6a65-4f7b-a9c7-1c7ef74a9ba4 with a value of 1. Test in audit mode (2) first. Local alternative (writes Defender preferences, not the Group Policy value this audit reads): Add-MpPreference -AttackSurfaceReductionRules_Ids b2b3f03d-6a65-4f7b-a9c7-1c7ef74a9ba4 -AttackSurfaceReductionRules_Actions 1
Properties
- Operating systems
- Any
- Tags
- defenderantiviruscis-l1
- Reference
- CIS Microsoft Defender Antivirus Benchmark v1.0.0 - 1.6.1.15 Ensure 'Configure Attack Surface Reduction rules: Set the state for each ASR rule' is set to 'b2b3f03d-6a65-4f7b-a9c7- 1c7ef74a9ba4:1'
Check this host
Run this on a machine you are allowed to audit. The scan is read-only.
tmaegis scan --target defender