How to block connection to non-domain networks via GPO

In the landscape of enterprise IT management, securing network connections is a top priority. One aspect of this is preventing domain-joined computers from connecting to non-domain networks, which can be a significant security risk. This guide provides a comprehensive walkthrough for system administrators on how to block connections to non-domain networks using Group Policy in a Windows domain environment.

Understanding the Need for Blocking Non-Domain Network Connections

Non-domain networks, such as public Wi-Fi or home networks, can pose various security threats including exposure to unsecured or malicious networks. So, blocking these connections ensures that domain-joined devices adhere to the security protocols and standards set by the organization.

Prerequisites

• Domain Administrator Privileges: You need to have domain administrator privileges to access and modify Group Policy Objects (GPOs).
• Group Policy Management Console (GPMC): Ensure GPMC is installed in your environment.

Step-by-Step Instructions

Step 1: Open Group Policy Management Console

Launch the GPMC by searching for “Group Policy Management” in the Start menu or by running gpmc.msc in the Run dialog.

Step 2: Create or Edit a Group Policy Object

• To create a new GPO, right-click on the domain or an Organizational Unit (OU) and select “Create a GPO in this domain, and Link it here…”.
• To modify an existing GPO, find it under the relevant domain or OU, right-click on it, and choose “Edit”.

Step 3: Navigate to Network Policy Settings

In the Group Policy Management Editor, go to: Computer Configuration → Policies → Windows Settings → Security Settings → Network List Manager Policies.

Step 4: Configuring Policies for Networks

• Here, you will see configurations for different network types (e.g., Domain, Private, Public).
• Now, right-click on “Unidentified Networks” and select “Properties”.

Step 5: Set the Location Type

• In the properties window, under the “Location type” section, select “Private”.
• This setting will treat all unidentified networks as private.

Step 6: Configuring Network Options

• Under the “User permissions” section, choose “User cannot change location”.
• This prevents users from manually changing the network type.

Step 7: Apply the Policy

• Click “OK” to apply these settings.
• Close the Group Policy Management Editor.
• The policy will apply at the next Group Policy refresh cycle. To expedite, you can use gpupdate /force on client machines.

Advanced Configuration and Use Cases

1. Specific Network Allowances: In some scenarios, you might want to allow specific non-domain networks (like trusted external networks). This can be configured by creating additional policies within the Network List Manager Policies.
2. Use Case – Remote Workers: For remote workers, enforce VPN usage by blocking connections to public networks, ensuring they connect to the domain network for access to resources.
3. Use Case – Enhanced Security Posture: In high-security environments, such as financial or government institutions, blocking non-domain networks can significantly mitigate the risk of data breaches or cyber-attacks.

Security Considerations

• Regular Policy Review: Regularly review the network policies to ensure they are aligned with current security needs and organizational policies.
• User Training and Awareness: Educate users about the risks of unsecured networks and the rationale behind restricting network connections.
• Compliance and Auditing: Ensure the policy aligns with compliance requirements and is included in security audits.

Troubleshooting

• Connectivity Issues: If users report connectivity issues, verify the network categorization and ensure the policy is being applied correctly.
• Policy Application: Use tools like Resultant Set of Policy (RSoP) or gpresult to troubleshoot issues related to GPO application.

Conclusion

Blocking connections to non-domain networks via Group Policy is an essential strategy for securing enterprise IT environments. This approach not only enhances network security but also ensures compliance with organizational IT policies. By following the steps outlined in this guide, system administrators can effectively manage network access and mitigate potential security risks associated with non-domain networks.