How to stop VPNs and tunnels from bypassing your filter

A VPN is the cleanest way past a filter: the device opens an encrypted tunnel to a server elsewhere, and both the traffic and the DNS lookups travel inside it. No amount of DNS filtering can see or stop that.

Where to intervene

• Tunnel ports. VPN protocols have well-known ports. Block them and most consumer VPN apps stop working.
• Public encrypted-DNS providers. DoH and DoT to a public resolver bypass DNS filtering without a full VPN.
• Strict mode. Refuse connections the router cannot identify, so traffic cannot hide behind a bare address.

The honest limits

No network filter is unbeatable — a determined user can rent a server and speak on any port. But the goal is not perfection; it is to make the common, one-tap bypass routes fail. That is what a guard layer does: close the channels that free VPN apps rely on. See how this fits a wider venue security setup.