windows-itpro-docs/windows/security/threat-protection/microsoft-defender-atp/customize-attack-surface-reduction.md

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title	description	keywords	search.product	ms.pagetype	ms.prod	ms.mktglfcycl	ms.sitesec	ms.pagetype	ms.localizationpriority	audience	author	ms.author	ms.date	ms.reviewer	manager
Configure how attack surface reduction rules work to fine-tune protection in your network	You can individually set rules in audit, block, or disabled modes, and add files and folders that should be excluded from ASR	Attack surface reduction, hips, host intrusion prevention system, protection rules, anti-exploit, antiexploit, exploit, infection prevention, customize, configure, exclude	eADQiWindows 10XVcnh	security	w10	manage	library	security	medium	ITPro	levinec	ellevin	05/13/2019		dansimp

Customize attack surface reduction rules

Applies to:

• Microsoft Defender Advanced Threat Protection (Microsoft Defender ATP)

Important

Some information relates to prereleased product which may be substantially modified before it's commercially released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Attack surface reduction rules help prevent software behaviors that are often abused to compromise your device or network. For example, an attacker might try to run an unsigned script off of a USB drive, or have a macro in an Office document make calls directly to the Win32 API. Attack surface reduction rules can constrain these kinds of risky behaviors and improve your organization's defensive posture.

Learn how to customize attack surface reduction rules by excluding files and folders or adding custom text to the notification alert that appears on a user's computer.

Attack surface reduction rules are supported on Windows 10, versions 1709 and 1803 or later, Windows Server, version 1803 (Semi-Annual Channel) or later, and Windows Server 2019. You can use Group Policy, PowerShell, and MDM CSPs to configure these settings.

Exclude files and folders

You can exclude files and folders from being evaluated by attack surface reduction rules. This means that even if an attack surface reduction rule detects that the file contains malicious behavior, the file will not be blocked from running.

Warning

This could potentially allow unsafe files to run and infect your devices. Excluding files or folders can severely reduce the protection provided by attack surface reduction rules. Files that would have been blocked by a rule will be allowed to run, and there will be no report or event recorded.

An exclusion applies to all rules that allow exclusions. You can specify an individual file, folder path, or the fully qualified domain name for a resource, but you cannot limit an exclusion to a specific rule.

An exclusion is applied only when the excluded application or service starts. For example, if you add an exclusion for an update service that is already running, the update service will continue to trigger events until the service is stopped and restarted.

Attack surface reduction supports environment variables and wildcards. For information about using wildcards, see Use wildcards in the file name and folder path or extension exclusion lists. If you are encountering problems with rules detecting files that you believe should not be detected, you should use audit mode to test the rule.

Rule description	GUID
Block all Office applications from creating child processes	D4F940AB-401B-4EFC-AADC-AD5F3C50688A
Block execution of potentially obfuscated scripts	5BEB7EFE-FD9A-4556-801D-275E5FFC04CC
Block Win32 API calls from Office macro	92E97FA1-2EDF-4476-BDD6-9DD0B4DDDC7B
Block Office applications from creating executable content	3B576869-A4EC-4529-8536-B80A7769E899
Block Office applications from injecting code into other processes	75668C1F-73B5-4CF0-BB93-3ECF5CB7CC84
Block JavaScript or VBScript from launching downloaded executable content	D3E037E1-3EB8-44C8-A917-57927947596D
Block executable content from email client and webmail	BE9BA2D9-53EA-4CDC-84E5-9B1EEEE46550
Block executable files from running unless they meet a prevalence, age, or trusted list criteria	01443614-cd74-433a-b99e-2ecdc07bfc25
Use advanced protection against ransomware	c1db55ab-c21a-4637-bb3f-a12568109d35
Block credential stealing from the Windows local security authority subsystem (lsass.exe)	9e6c4e1f-7d60-472f-ba1a-a39ef669e4b2
Block process creations originating from PSExec and WMI commands	d1e49aac-8f56-4280-b9ba-993a6d77406c
Block untrusted and unsigned processes that run from USB	b2b3f03d-6a65-4f7b-a9c7-1c7ef74a9ba4
Block Office communication applications from creating child processes	26190899-1602-49e8-8b27-eb1d0a1ce869
Block Adobe Reader from creating child processes	7674ba52-37eb-4a4f-a9a1-f0f9a1619a2c
Block persistence through WMI event subscription	e6db77e5-3df2-4cf1-b95a-636979351e5b

See the attack surface reduction topic for details on each rule.

Use Group Policy to exclude files and folders

1. On your Group Policy management computer, open the Group Policy Management Console, right-click the Group Policy Object you want to configure and click Edit.

2. In the Group Policy Management Editor go to Computer configuration and click Administrative templates.

3. Expand the tree to Windows components > Windows Defender Antivirus > Windows Defender Exploit Guard > Attack surface reduction.

4. Double-click the Exclude files and paths from Attack surface reduction Rules setting and set the option to Enabled. Click Show and enter each file or folder in the Value name column. Enter 0 in the Value column for each item.

Warning

Do not use quotes as they are not supported for either the Value name column or the Value column.

Use PowerShell to exclude files and folders

1. Type powershell in the Start menu, right-click Windows PowerShell and click Run as administrator

2. Enter the following cmdlet:

   Add-MpPreference -AttackSurfaceReductionOnlyExclusions "<fully qualified path or resource>"
   

Continue to use Add-MpPreference -AttackSurfaceReductionOnlyExclusions to add more folders to the list.

Important

Use Add-MpPreference to append or add apps to the list. Using the Set-MpPreference cmdlet will overwrite the existing list.

Use MDM CSPs to exclude files and folders

Use the ./Vendor/MSFT/Policy/Config/Defender/AttackSurfaceReductionOnlyExclusions configuration service provider (CSP) to add exclusions.

Customize the notification

See the Windows Security topic for more information about customizing the notification when a rule is triggered and blocks an app or file.

Related topics

• Reduce attack surfaces with attack surface reduction rules
• Enable attack surface reduction rules
• Evaluate attack surface reduction rules
• Attack surface reduction FAQ