Solving Windows 11 Windows Defender Application Control and Device Guard Policy Configuration and Troubleshooting

Understanding Windows Defender Application Control (WDAC) and Device Guard

In the ever-evolving landscape of cybersecurity, Microsoft has introduced robust tools to protect devices against malware and unauthorized software. Two such solutions are Windows Defender Application Control (WDAC) and Device Guard, which have now been combined under the WDAC umbrella.

WDAC is a software-based security layer that enforces an explicit list of approved software that can run on a device. It ensures that only trusted applications, known to the organization, are allowed to execute. This approach helps mitigate the risk of malicious code running on managed devices.

On the other hand, Device Guard, now integrated into WDAC, provides hardware-based security features to further strengthen the protection against unauthorized software execution. By leveraging the device’s virtualization-based security capabilities, Device Guard can create a secure environment to enforce WDAC policies.

Configuring WDAC Policies with Configuration Manager

As an experienced IT professional, you can leverage Microsoft Configuration Manager to deploy and manage WDAC policies across your organization. This approach offers several benefits, including centralized policy management, enforcement, and monitoring.

Deploying WDAC Policies

1. Create an Application Control Policy: In the Configuration Manager console, navigate to the Assets and Compliance workspace, expand Endpoint Protection, and select the Windows Defender Application Control node. On the Home tab, click “Create Application Control Policy” to initiate the policy creation process.

2. Define Policy Settings: On the General page of the wizard, specify a unique name and an optional description for the policy. Choose the desired enforcement mode, such as “Enforcement Enabled” (only trusted applications can run) or “Audit Only” (log untrusted programs but allow them to run).

3. Manage Trusted Software: On the Inclusions tab, you can choose to authorize software trusted by the Intelligent Security Graph or manually add specific files or folders to be trusted. This can help overcome issues with managed installer behaviors or trust line-of-business applications.

4. Deploy the Policy: After completing the wizard, select the policy in the console and click “Deploy Application Control Policy” from the Deployment group on the Home tab. Choose the target collection and configure the deployment schedule, ensuring clients can evaluate the policy outside of any maintenance windows.

Monitoring WDAC Policy Compliance

To ensure the deployed WDAC policy is being correctly applied, you can leverage the information provided in the Monitor compliance settings article. This includes:

1. Policy Processing Logs: Check the %WINDIR%\CCM\Logs\DeviceGuardHandler.log file on client devices to monitor the processing of the Application Control policy.

2. Event Logs: Review the following event logs to verify the specific software being blocked or audited:

3. For executable files: Applications and Services Logs > Microsoft > Windows > Code Integrity > Operational
4. For Windows Installer and script files: Applications and Services Logs > Microsoft > Windows > AppLocker > MSI and Script

By closely monitoring the policy deployment and its enforcement, you can identify any issues and make necessary adjustments to ensure the effectiveness of your WDAC implementation.

Troubleshooting WDAC and Device Guard Deployment Challenges

While WDAC and Device Guard are powerful tools for securing your Windows environment, you may encounter deployment and configuration challenges. Let’s explore some common issues and their resolutions.

Devices Unable to Process WDAC Policies

If devices are unable to process the deployed WDAC policies, consider the following troubleshooting steps:

1. Verify Device Compatibility: Ensure the target devices meet the minimum Windows version and SKU requirements for WDAC support. Refer to the Windows Defender Application Control deployment guide for the latest information.

2. Check Restart Configuration: Verify that the “Enforce a restart of devices so that this policy can be enforced for all processes” option is enabled during policy deployment. This ensures that the new policy is applied to all running processes on the device.

3. Adjust Compliance Evaluation Schedule: If you notice issues in policy processing, configure the compliance evaluation schedule to be more frequent, such as every hour. This can help clients reattempt to process the WDAC policy in case of initial failures.

4. Exclude Application Control from Certain Processes: Certain processes, such as HTML applications with the .hta file extension, are automatically blocked by WDAC policies. You may need to create exclusions or adjust the policy to accommodate specific application requirements.

Devices Unable to Run Trusted Applications

In some cases, users may encounter issues where trusted applications are blocked by the WDAC policy. This can happen when the policy is deployed in “Enforcement Enabled” mode without proper preparation.

1. Prepare Devices in a Lab Environment: Before deploying an “Enforcement Enabled” policy to production devices, first test the policy in a lab environment. Deploy the policy, restart the devices, and verify that all trusted applications are allowed to run as expected.

2. Avoid Switching Between Enforcement Modes: Do not deploy a policy with “Enforcement Enabled” and then later deploy a policy with “Audit Only” mode to the same device. This configuration can result in untrusted software being allowed to run, compromising the security measures.

3. Leverage Configuration Manager as a Managed Installer: When using Configuration Manager to enable WDAC, the policy leverages a Windows AppLocker policy to identify managed installers. However, the actual enforcement happens through the WDAC policy, not AppLocker. Ensure that Configuration Manager is properly set up as a managed installer on the devices.

Devices Unable to Run Applications Due to Restricted App Execution

In some cases, you may encounter a scenario where devices are unable to launch applications, with an error message indicating that “Your Organization used Device Guard to block this app.” This issue may not be directly related to WDAC or Device Guard policies.

1. Investigate Restricted App Execution Setting: Check the Microsoft Defender Security Center portal for the affected devices. Look for a menu item related to “Restrict App Execution” and ensure it is not enabled on the devices.

2. Disable Restricted App Execution: If the “Restrict App Execution” setting is enabled, disable it on the affected devices. This should restore the normal functionality and allow applications to run without the “Device Guard” error message.

3. Identify the Source of the Restricted App Execution Setting: Determine how the “Restrict App Execution” setting was enabled on the affected devices in the first place, as it may have been configured through a policy or other management tool. Investigate and address the root cause to prevent the issue from recurring.

By understanding the common challenges and following these troubleshooting steps, you can effectively deploy and manage WDAC and Device Guard policies within your organization, ensuring that your devices are protected against malware and unauthorized software execution.

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