Yep, I can ping 8.8.8.8. Only when I'm logged in with my ticket, not when I'm just connected to the LAN without being logged in. I don't know what that means, this is the first I hear of this 8.8.8.8 IP. I notice that some web pages are restricted, when I try to visit them I get redirected to a block.opendns.com page. When I'm not logged in with a ticket (or username + pass) and I try to access the internet, wireshark shows DNS requests being sent between my IP and 192.168.137.1. Do these details back up your theory that they are using DNS filtering? Would that mean this Antamedia system works by directing all DNS requests to 192.168.137.1, then checking to see if there is an active ticket/username session, before responding to the DNS request? I'll look into DNS tunneling but I don't think I'm knowledgeable enough yet to be able to figure out what to do here.
I don't know what a TCP handshake is yet, I'll have to look that up. The Vista machine has plenty of open ports, I haven't checked for any vulnerabilities yet. The login page is plain HTTP.
I bet I can hijack other peoples tickets by ARP spoofing an IP that is logged in with their ticket, but that would be sloppy and I wouldn't want to steal other peoples time like that. Brute forcing a ticket would be sloppy too, and they would rapidly figure out that someone is stealing tickets. Plus, most of these tickets are 8 chars long, so it would take me an ungodly amount of attempts before hitting a correct combination of chars. If I was the admin, I would ban any MAC address that makes more than 20 consecutive wrong attempts.