I vaguely recall a story from a long time ago when companies like AOL and CompuServe sent you CDs in the mail with demo versions of their products. You could di

I vaguely recall a story from a long time ago when companies like AOL and CompuServe sent you CDs in the mail with demo versions of their products. You could dial up using them and access a subset of their services before purchasing full access. Someone figured out that although the rest of the internet was firewalled, they still relayed DNS requests to the original DNS servers (maybe needing a low TTL) and used this to tunnel via a custom DNS server. Et voilà! Free ISP :)