Windows Defender AV must be configured to block execution of potentially obfuscated scripts.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-77975	WNDF-AV-000037	SV-92671r1_rule		Medium

Description
Malware and other threats can attempt to obfuscate or hide their malicious code in some script files. This rule prevents scripts that appear to be obfuscated from running. It uses the AntiMalwareScanInterface (AMSI) to determine if a script is potentially obfuscated, and then blocks such a script, or blocks scripts when an attempt is made to access them.

STIG	Date
MS Windows Defender Antivirus Security Technical Implementation Guide	2020-05-12

Details

Check Text ( C-77585r1_chk )
This setting is applicable starting with v1709 of Windows 10, it is NA for prior versions. Verify the policy value for Computer Configuration -> Administrative Templates -> Windows Components -> Windows Defender Antivirus -> Windows Defender Exploit Guard -> Attack Surface Reduction -> "Configure Attack Surface Reduction rules" is set to "Enabled”. Click ‘Show...’. Verify the rule ID in the Value name column and the desired state in the Value column is set as follows: Value name: 5BEB7EFE-FD9A-4556-801D-275E5FFC04CC Value: 1 Procedure: Use the Windows Registry Editor to navigate to the following key: HKLM\Software\Policies\Microsoft\Windows Defender\Windows Defender Exploit Guard\ASR\Rules Criteria: If the value “5BEB7EFE-FD9A-4556-801D-275E5FFC04CC” is REG_SZ = 1, this is not a finding.

Check Text ( C-77585r1_chk )

This setting is applicable starting with v1709 of Windows 10, it is NA for prior versions.

Verify the policy value for Computer Configuration -> Administrative Templates -> Windows Components -> Windows Defender Antivirus -> Windows Defender Exploit Guard -> Attack Surface Reduction -> "Configure Attack Surface Reduction rules" is set to "Enabled”. Click ‘Show...’. Verify the rule ID in the Value name column and the desired state in the Value column is set as follows:
Value name: 5BEB7EFE-FD9A-4556-801D-275E5FFC04CC
Value: 1

Procedure: Use the Windows Registry Editor to navigate to the following key:
HKLM\Software\Policies\Microsoft\Windows Defender\Windows Defender Exploit Guard\ASR\Rules

Criteria: If the value “5BEB7EFE-FD9A-4556-801D-275E5FFC04CC” is REG_SZ = 1, this is not a finding.

Fix Text (F-84687r1_fix)
Set the policy value for Computer Configuration -> Administrative Templates -> Windows Components -> Windows Defender Antivirus -> Windows Defender Exploit Guard -> Attack Surface Reduction -> "Configure Attack Surface Reduction rules" to "Enabled”. Click ‘Show...’. Set the Value name to “5BEB7EFE-FD9A-4556-801D-275E5FFC04CC” and the Value to “1”.