Frequently asked questions - Microsoft Defender Application Guard

Applies to: Microsoft Defender for Endpoint

Answering frequently asked questions about Microsoft Defender Application Guard (Application Guard) features, integration with the Windows operating system, and general configuration.

Frequently Asked Questions

Can I enable Application Guard on machines equipped with 4-GB RAM?

We recommend 8-GB RAM for optimal performance but you can use the following registry DWORD values to enable Application Guard on machines that aren't meeting the recommended hardware configuration.

HKLM\software\Microsoft\Hvsi\SpecRequiredProcessorCount (Default is four cores.)

HKLM\software\Microsoft\Hvsi\SpecRequiredMemoryInGB (Default is 8 GB.)

HKLM\software\Microsoft\Hvsi\SpecRequiredFreeDiskSpaceInGB (Default is 5 GB.)

Can employees download documents from the Application Guard Edge session onto host devices?

In Windows 10 Enterprise edition 1803, users are able to download documents from the isolated Application Guard container to the host PC. This capability is managed by policy.

In Windows 10 Enterprise edition 1709 or Windows 10 Professional edition 1803, it is not possible to download files from the isolated Application Guard container to the host PC. However, employees can use the Print as PDF or Print as XPS options and save those files to the host device.

Can employees copy and paste between the host device and the Application Guard Edge session?

Depending on your organization's settings, employees can copy and paste images (.bmp) and text to and from the isolated container.

Why don't employees see their Favorites in the Application Guard Edge session?

To help keep the Application Guard Edge session secure and isolated from the host device, we don't copy the Favorites stored in the Application Guard Edge session back to the host device.

Why aren’t employees able to see their Extensions in the Application Guard Edge session?

Currently, the Application Guard Edge session doesn't support Extensions. However, we're closely monitoring your feedback about this.

How do I configure Microsoft Defender Application Guard to work with my network proxy (IP-Literal Addresses)?

Microsoft Defender Application Guard requires proxies to have a symbolic name, not just an IP address. IP-Literal proxy settings such as 192.168.1.4:81 can be annotated as itproxy:81 or using a record such as P19216810010 for a proxy with an IP address of 192.168.100.10. This applies to Windows 10 Enterprise edition 1709 or higher. These would be for the proxy policies under Network Isolation in Group Policy or Intune.

Which Input Method Editors (IME) in 19H1 are not supported?

The following Input Method Editors (IME) introduced in Windows 10, version 1903 are currently not supported in Microsoft Defender Application Guard.

  • Vietnam Telex keyboard
  • Vietnam number key-based keyboard
  • Hindi phonetic keyboard
  • Bangla phonetic keyboard
  • Marathi phonetic keyboard
  • Telugu phonetic keyboard
  • Tamil phonetic keyboard
  • Kannada phonetic keyboard
  • Malayalam phonetic keyboard
  • Gujarati phonetic keyboard
  • Odia phonetic keyboard
  • Punjabi phonetic keyboard

I enabled the hardware acceleration policy on my Windows 10 Enterprise, version 1803 deployment. Why are my users still only getting CPU rendering?

This feature is currently experimental only and is not functional without an additional registry key provided by Microsoft. If you would like to evaluate this feature on a deployment of Windows 10 Enterprise, version 1803, contact Microsoft and we’ll work with you to enable the feature.

What is the WDAGUtilityAccount local account?

This account is part of Application Guard beginning with Windows 10, version 1709 (Fall Creators Update). This account remains disabled until Application Guard is enabled on your device. This item is integrated to the OS and is not considered as a threat/virus/malware.

How do I trust a subdomain in my site list?

To trust a subdomain, you must precede your domain with two dots, for example: ..contoso.com ensures that mail.contoso.com or news.contoso.com are trusted. The first dot represents the strings for the subdomain name (mail or news), the second dot recognizes the start of the domain name (contoso.com). This prevents sites such as fakesitecontoso.com from being trusted.

Are there differences between using Application Guard on Windows Pro vs Windows Enterprise?

When using Windows Pro or Windows Enterprise, you have access to using Application Guard in Standalone Mode. However, when using Enterprise you have access to Application Guard in Enterprise-Managed Mode. This mode has some extra features that the Standalone Mode does not. For more information, see Prepare to install Microsoft Defender Application Guard.

Is there a size limit to the domain lists that I need to configure?

Yes, both the Enterprise Resource domains hosted in the cloud and the Domains categorized as both work and personal have a 16383-B limit.

Why does my encryption driver break Microsoft Defender Application Guard?

Microsoft Defender Application Guard accesses files from a VHD mounted on the host that needs to be written during setup. If an encryption driver prevents a VHD from being mounted or from being written to, Application Guard does not work and results in an error message (0x80070013 ERROR_WRITE_PROTECT).

Why do the Network Isolation policies in Group Policy and CSP look different?

There is not a one-to-one mapping among all the Network Isolation policies between CSP and GP. Mandatory network isolation policies to deploy Application Guard are different between CSP and GP.

Mandatory network isolation GP policy to deploy Application Guard: "DomainSubnets or CloudResources" Mandatory network isolation CSP policy to deploy Application Guard: "EnterpriseCloudResources or (EnterpriseIpRange and EnterpriseNetworkDomainNames)" For EnterpriseNetworkDomainNames, there is no mapped CSP policy.

Microsoft Defender Application Guard accesses files from a VHD mounted on the host that needs to be written during setup. If an encryption driver prevents a VHD from being mounted or from being written to, Application Guard does not work and results in an error message (0x80070013 ERROR_WRITE_PROTECT).

Why did Application Guard stop working after I turned off hyperthreading?

If hyperthreading is disabled (because of an update applied through a KB article or through BIOS settings), there is a possibility Application Guard no longer meets the minimum requirements.

Why am I getting the error message "ERROR_VIRTUAL_DISK_LIMITATION"?

Application Guard might not work correctly on NTFS compressed volumes. If this issue persists, try uncompressing the volume.

Why am I getting the error message "ERR_NAME_NOT_RESOLVED" after not being able to reach PAC file?

This is a known issue. To mitigate this you need to create two firewall rules. For guidance on how to create a firewall rule by using group policy, see:

First rule (DHCP Server):

  1. Program path: %SystemRoot%\System32\svchost.exe
  2. Local Service: Sid: S-1-5-80-2009329905-444645132-2728249442-922493431-93864177 (Internet Connection Service (SharedAccess))
  3. Protocol UDP
  4. Port 67

Second rule (DHCP Client) This is the same as the first rule, but scoped to local port 68. In the Microsoft Defender Firewall user interface go through the following steps:

  1. Right click on inbound rules, create a new rule.
  2. Choose custom rule.
  3. Program path: %SystemRoot%\System32\svchost.exe.
  4. Protocol Type: UDP, Specific ports: 67, Remote port: any.
  5. Any IP addresses.
  6. Allow the connection.
  7. All profiles.
  8. The new rule should show up in the user interface. Right click on the rule > properties.
  9. In the Programs and services tab, Under the Services section click on settings. Choose Apply to this Service and select Internet Connection Sharing (ICS) Shared Access.

Why can I not launch Application Guard when Exploit Guard is enabled?

There is a known issue such that if you change the Exploit Protection settings for CFG and possibly others, hvsimgr cannot launch. To mitigate this issue, go to Windows Security > App and Browser control > Exploit Protection Setting, and then switch CFG to use default.

How can I have ICS in enabled state yet still use Application Guard?

ICS is enabled by default in Windows, and ICS must be enabled in order for Application Guard to function correctly. We do not recommend disabling ICS; however, you can disable ICS in part by using a Group Policy and editing registry keys.

  1. In the Group Policy setting called, Prohibit use of Internet Connection Sharing on your DNS domain network, set it to Disabled.

  2. Disable IpNat.sys from ICS load as follows:
    System\CurrentControlSet\Services\SharedAccess\Parameters\DisableIpNat = 1

  3. Configure ICS (SharedAccess) to enabled as follows:
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Start = 3

  4. (This is optional) Disable IPNAT as follows:
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\IPNat\Start = 4

  5. Reboot the device.

See also

Configure Microsoft Defender Application Guard policy settings