Virtual private networking (VPN) companies market their services as a way to prevent anyone from snooping on your Internet usage. But new research suggests this is a dangerous assumption when connecting to a VPN via an untrusted network, because attackers on the same network could force a target’s traffic off of the protection provided by their VPN without triggering any alerts to the user.
Full tunnel using routing wouldn’t work but many full tunnel implementations use a shim where once the Tunnel is connected, the system route table isn’t referenced anymore, so you can put as many static routes etc as you want, but all traffic will hit the VPN interface before routing is done. For example Cisco any connect removes route look-up from the TCP/IP stack of the local system.