Microsoft Defender AV must block Office communication application from creating child processes.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-278654	SRG-APP-000210	WNDF-AV-000050	SV-278654r1144047_rule	2025-11-25	2

Description
This policy setting prevents Outlook from creating child processes while still allowing legitimate Outlook functions. This rule protects against social engineering attacks and prevents exploiting code from abusing vulnerabilities in Outlook. It also protects against Outlook rules and forms exploits that attackers can use when a user's credentials are compromised.

ℹ️ Check
Verify the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> Microsoft Defender Exploit Guard >> Attack Surface Reduction >> Configure Attack Surface Reduction rules is set to "Enabled". 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 "26190899-1602-49e8-8b27-eb1d0a1ce869" is REG_SZ = 1, this is not a finding. If the value is other than 1, this is a finding.

ℹ️ Check

Verify the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> Microsoft Defender Exploit Guard >> Attack Surface Reduction >> Configure Attack Surface Reduction rules is set to "Enabled". 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 "26190899-1602-49e8-8b27-eb1d0a1ce869" is REG_SZ = 1, this is not a finding. If the value is other than 1, this is a finding.

✔️ Fix
Set the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> Microsoft Defender Exploit Guard >> Attack Surface Reduction >> Configure Attack Surface Reduction rules to "Enabled". Under the policy option "Set the state for each ASR rule:", then click "Show". Enter GUID "26190899-1602-49e8-8b27-eb1d0a1ce869" in the "Value Name" column. Enter "1" in the "Value" column. Click "OK". Click "Apply".

✔️ Fix

Set the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> Microsoft Defender Exploit Guard >> Attack Surface Reduction >> Configure Attack Surface Reduction rules to "Enabled". Under the policy option "Set the state for each ASR rule:", then click "Show". Enter GUID "26190899-1602-49e8-8b27-eb1d0a1ce869" in the "Value Name" column. Enter "1" in the "Value" column. Click "OK". Click "Apply".