Here are potential reasons why Sangfor NGAF and IAM might fail to block browser-based VPNs, along with troubleshooting steps:

1. Incomplete or Incorrect Configurations:

    URL Filtering:
        Ensure VPN-related URLs and categories are accurately blocked.
        Verify there are no exceptions or overrides allowing access.
    Application Control:
        Confirm rules cover specific VPN applications and their variants.
        Review application signatures for updates and accuracy.
    Anti-Proxy:
        Validate the feature is enabled and functioning correctly.
        Verify proxy detection methods are up-to-date.
    Application Containment:
        Ensure targeted VPN applications are included in the containment list.
        Review containment policies for any inconsistencies.

2. Signature Updates:

    Outdated Signatures:
        Regularly update NGAF and IAM signatures to identify new VPN providers and techniques.
        Subscribe to signature updates from Sangfor.

3. Technical Limitations:

    Evasion Techniques:
        Some VPNs use techniques like obfuscation or encryption to circumvent detection.
        Consult Sangfor support for guidance on addressing advanced evasion methods.
    Port Hopping:
        VPNs might switch ports dynamically to bypass blocking rules.
        Implement broader traffic inspection or consider advanced threat protection solutions.

4. User Circumvention:

    Unauthorized Software:
        Users might install unauthorized VPN software on personal devices or use external proxies.
        Enforce acceptable use policies and monitor network traffic for unusual patterns.

5. Configuration Conflicts:

    Overlapping Rules:
        Review NGAF and IAM configurations for conflicting rules that might inadvertently allow VPN traffic.

Troubleshooting Steps:

    Review Logs:
        Analyze NGAF and IAM logs to identify VPN traffic patterns and potential causes of failure.
    Test Blocking:
        Use a known browser-based VPN to verify if blocking is effective.
    Consult Documentation:
        Refer to Sangfor's documentation for troubleshooting guidance and best practices.
    Engage Support:
        If issues persist, contact Sangfor support for further assistance and analysis.

Additional Considerations:

    Layered Defense:
        Employ a multi-layered approach to VPN blocking, combining NGAF, IAM, and endpoint security measures.
    User Awareness:
        Educate users about VPN restrictions and the importance of security compliance.
    Stay Updated:
        Stay informed about new VPN technologies and techniques to adapt blocking strategies accordingly.

Ensure that your NGAF and IAM have the latest signatures and definitions for VPN applications. Regularly update the application and threat databases to stay ahead of new evasion techniques.