In this article

Block browser VPN and proxy features that can bypass DNS-based content filtering, including Opera, Google Chrome Data Saver, and the Puffin browser.

Opera desktop includes built-in VPN and proxy features, so DNSFilter does not recommend using Opera alongside DNSFilter products.

Block the domains listed in each section or use Threats category controls to reduce circumvention risk.

Block Opera VPN

To prevent Opera's built-in VPN from connecting, add this domain to the Block List:

• api.sec-tunnel.com

Block Opera Turbo and Opera Mini proxy traffic

Opera Mini, Opera for Android, and Opera desktop (Turbo Mode) use proxy-based traffic routing that may bypass DNS-based content filtering.

To block this behavior, use one of the following options:

• Enable Proxy and Filter Avoidance in the Threats tab of the Filtering Policy

• Add these domains to the Block List:

  • opera-mini.net

  • sitecheck2.opera.com

Block Google Chrome Data Saver proxy traffic

Google Chrome Data Saver is a proxy that compresses content before it reaches the device to reduce bandwidth usage and load content faster on mobile devices. It is especially useful on cellular 3G, 4G, and LTE connections because of the cost and speed of cellular bandwidth.

According to Google documentation, Data Saver is enabled by default on all Android devices. Availability depends on the Android version, device, and Google Chrome version. A Chrome plugin is also available for desktop operating systems.

With Data Saver enabled, DNS requests go directly through the proxy and circumvent DNSFilter policy enforcement.

To block this behavior, use one of the following options:

• Enable Proxy and Filter Avoidance in the Threats tab of the Filtering Policy
• Add these domains to the Block List:
  • googlezip.net
  • datasaver.googleapis.com

Block Puffin browser

Puffin is a server-side browser. It uses its own connection to servers run by CloudMosa, the company that produces Puffin, and depends on HTTPS communication with CloudMosa.

To block Puffin, add cloudmosa.net to the Block List. The browser then cannot trust the SSL certificate it uses for communication and hangs on startup.

To also prevent users from downloading the browser, add puffinbrowser.com to the Block List.