With the recent rise in awareness of HTTP session hijacking, surfing the internet on a public wireless network has become quite perilous. At my university, the wireless network is totally open --- no encryption at all. Students are encouraged to use VPN, but VPN disconnects when I shut my laptop's lid, and requires a password to reconnect.
Sometimes I don't remember to connect to VPN, and even when I do, I fear that open Facebook/Twitter/other tabs might silently make requests in the background, giving away my sessions before I have a chance to connect.
On Snow Leopard, how can I block any traffic from being transmitted over my wireless card until I am connected to VPN?
My school uses Cisco VPN client, if it matters.