Information
This rule blocks Office apps from creating child processes. Office apps include Word, Excel, PowerPoint, OneNote, and Access.
Rule ID and name:
- d4f940ab-401b-4efc-aadc-ad5f3c50688a (Block all Office applications from creating child processes)
The recommended state for this setting is: d4f940ab-401b-4efc-aadc-ad5f3c50688a:2 (Audit) or higher. Configuring this setting to d4f940ab-401b-4efc-aadc-ad5f3c50688a:1 (Block) also conforms to the benchmark.
Note: More information on ASR rules can be found at the following link: Use Attack surface reduction rules to prevent malware infection | Microsoft Docs https://docs.microsoft.com/en-us/windows/security/threat-protection/windows-defender-exploit-guard/attack-surface-reduction-exploit-guard
Attack surface reduction helps prevent actions and apps that are typically used by exploit-seeking malware to infect machines.
Creating malicious child processes is a common malware strategy. Malware that abuses Office as a vector often runs VBA macros and exploit code to download and attempt to run more payloads. However, some legitimate line-of-business applications might also generate child processes for benign purposes, such as spawning a command prompt or using PowerShell to configure registry settings.
Solution
To establish the recommended configuration via GP, set the following UI path to d4f940ab-401b-4efc-aadc-ad5f3c50688a with a value of 2 or 1 :
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
Note: This Group Policy path is provided by the Group Policy template WindowsDefender.admx/adml that is included with the Microsoft Windows 10 Release 1709 Administrative Templates (or newer).
Impact:
When a rule is triggered, a notification will be displayed from the Action Center.
Warning: Prior to configuring this rule in Block mode, it should be enabled in Audit mode to verify that it does not introduce issues, especially for Microsoft Outlook.