Enable attack surface reduction rules

Attack surface reduction rules help prevent actions and apps that malware often uses to infect computers. You can set attack surface reduction rules for computers running Windows 10 or Windows Server 2019.

To use ASR rules, you need either a Windows 10 Enterprise E3 or E5 license. We recommend an E5 license so you can take advantage of the advanced monitoring and reporting capabilities available in Windows Defender Advanced Threat Protection (Windows Defender ATP). These advanced capabilities aren't available with an E3 license, but you can develop your own monitoring and reporting tools to use in conjunction with ASR rules.

Exclude files and folders from ASR rules

You can exclude files and folders from being evaluated by most attack surface reduction rules. This means that even if an ASR rule determines the file or folder contains malicious behavior, it will not block the file from running. This could potentially allow unsafe files to run and infect your devices.

Warning

Excluding files or folders can severely reduce the protection provided by ASR rules. Excluded files will be allowed to run, and no report or event will be recorded.

If ASR rules are detecting files that you believe shouldn't be detected, you should use audit mode first to test the rule.

Important

File and folder exclusions do not apply to the following ASR rules:

  • Block process creations originating from PSExec and WMI commands
  • Block JavaScript or VBScript from launching downloaded executable content

You can specify individual files or folders (using folder paths or fully qualified resource names) but you can't specify which rules the exclusions apply to.

Important

The rule Block executable files from running unless they meet a prevalence, age, or trusted list criterion with GUID 01443614-cd74-433a-b99e-2ecdc07bfc25 is owned by Microsoft and is not specified by admins. It uses cloud-delivered protection to update its trusted list regularly.

ASR rules support environment variables and wildcards. For information about using wildcards, see Use wildcards in the file name and folder path or extension exclusion lists.

The following procedures for enabling ASR rules include instructions for how to exclude files and folders.

Enable and audit attack surface reduction rules

It's best to use an enterprise-level management platform like Intune or System Center Configuration Manager (SCCM) to configure ASR rules, but you can also use Group Policy, PowerShell, or third-party mobile device management (MDM) CSPs.

Warning

If you manage your computers and devices with Intune, SCCM, or other enterprise-level management platform, the management software will overwrite any conflicting Group Policy or PowerShell settings on startup.

For a complete list of ASR rules, see Reduce attack surfaces with attack surface reduction rules.

Each ASR rule contains three settings:

  • Not configured: Disable the ASR rule
  • Block: Enable the ASR rule
  • Audit: Evaluate how the ASR rule would impact your organization if enabled

For further details on how audit mode works and when to use it, see Audit Windows Defender Exploit Guard.

Enable ASR rules in Intune

  1. In Intune, select Device configuration > Profiles. Choose an existing endpoint protection profile or create a new one. To create a new one, select Create profile and enter information for this profile. For Profile type, select Endpoint protection. If you've chosen an existing profile, select Properties and then select Settings.

  2. In the Endpoint protection pane, select Windows Defender Exploit Guard, then select Attack Surface Reduction. Select the desired setting for each ASR rule.

  3. Under Attack Surface Reduction exceptions, you can enter individual files and folders, or you can select Import to import a CSV file that contains files and folders to exclude from ASR rules. Each line in the CSV file should be in the following format:

  4. Select OK on the three configuration panes and then select Create if you're creating a new endpoint protection file or Save if you're editing an existing one.

Enable ASR rules in SCCM

For information about enabling ASR rules and setting exclusions in SCCM, see Create and deploy an Exploit Guard policy.

Enable ASR rules with Group Policy

Warning

If you manage your computers and devices with Intune, SCCM, or other enterprise-level management platform, the management software will overwrite any conflicting Group Policy settings on startup.

  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. Select Configure Attack surface reduction rules and select Enabled. You can then set the individual state for each rule in the options section:

    • Click Show... and enter the rule ID in the Value name column and your desired state in the Value column as follows:

      • Disable = 0
      • Block (enable ASR rule) = 1
      • Audit = 2

      Group policy setting showing a blank attack surface reduction rule ID and value of 1

  5. To exclude files and folders from ASR rules, select 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.

Enable ASR rules with PowerShell

Warning

If you manage your computers and devices with Intune, SCCM, or other enterprise-level management platform, the management software will overwrite any conflicting PowerShell settings on startup.

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

  2. Enter the following cmdlet:

    Set-MpPreference -AttackSurfaceReductionRules_Ids <rule ID> -AttackSurfaceReductionRules_Actions Enabled
    

    To enable ASR rules in audit mode, use the following cmdlet:

    Add-MpPreference -AttackSurfaceReductionRules_Ids <rule ID> -AttackSurfaceReductionRules_Actions AuditMode
    

    To turn off ASR rules, use the following cmdlet:

    Add-MpPreference -AttackSurfaceReductionRules_Ids <rule ID> -AttackSurfaceReductionRules_Actions Disabled
    

    Important

    You must specify the state individually for each rule, but you can combine rules and states in a comma-separated list.

    In the following example, the first two rules will be enabled, the third rule will be disabled, and the fourth rule will be enabled in audit mode:

    Set-MpPreference -AttackSurfaceReductionRules_Ids <rule ID 1>,<rule ID 2>,<rule ID 3>,<rule ID 4> -AttackSurfaceReductionRules_Actions Enabled, Enabled, Disabled, AuditMode
    

    You can also the Add-MpPreference PowerShell verb to add new rules to the existing list.

    Warning

    Set-MpPreference will always overwrite the existing set of rules. If you want to add to the existing set, you should use Add-MpPreference instead. You can obtain a list of rules and their current state by using Get-MpPreference

  3. To exclude files and folders from ASR rules, use the following cmdlet:

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

    Continue to use Add-MpPreference -AttackSurfaceReductionOnlyExclusions to add more files and 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.

Enable ASR rules with MDM CSPs

Use the ./Vendor/MSFT/Policy/Config/Defender/AttackSurfaceReductionRules configuration service provider (CSP) to individually enable and set the mode for each rule.

The following is a sample for reference, using GUID values for ASR rules.

OMA-URI path: ./Vendor/MSFT/Policy/Config/Defender/AttackSurfaceReductionRules

Value: {75668C1F-73B5-4CF0-BB93-3ECF5CB7CC84}=2|{3B576869-A4EC-4529-8536-B80A7769E899}=1|{D4F940AB-401B-4EfC-AADC-AD5F3C50688A}=2|{D3E037E1-3EB8-44C8-A917-57927947596D}=1|{5BEB7EFE-FD9A-4556-801D-275E5FFC04CC}=0|{BE9BA2D9-53EA-4CDC-84E5-9B1EEEE46550}=1

The values to enable, disable, or enable in audit mode are:

  • Disable = 0
  • Block (enable ASR rule) = 1
  • Audit = 2

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

Example:

OMA-URI path: ./Vendor/MSFT/Policy/Config/Defender/AttackSurfaceReductionOnlyExclusions

Value: c:\path|e:\path|c:\Whitelisted.exe

Note

Be sure to enter OMA-URI values without spaces.