freeze is susposed to make you go back to the screen, its a punishment you get by hacking.

If he got out of Minecraft (so fully closed the client) then trust me: he also left the game (server). I get the impression that there wasn't really much "hacking" going on, it sounds more like flooding to me. Providing a server with so much garbage that it eventually lags out the whole thing.

As to legal or not... impossible to tell without knowing exactly what he was doing. But from the sound of things it most certainly wasn't ethical, and as Ezacu said: you might want to be more careful because if he's using your Internet connection then chances are high that you'll be held responsible for his actions.

How was he hacking, hacking like on a minecraft hack client or hacking like actually hacking. It would be illegal if he is actually hacking but if you are just using a hack client or mods then it is not illegal but I would definitely not advise ever using hacks. Most minecraft servers do not allow hacks which will get you banned if you do use them and hacks really take the fun out of the game for both you and other players. If you can't get out of the game press ALT-F4 on windows and force quit minecraft on Mac. Other than that just shut down your computer. Also, just for future reference, make your title a little more descriptive such as, "Please Help, Minecraft Frozen" because you already are in the minecraft help forum so people know that you need help. If you need any more help pm me soon because in an hour or so I won't really be able to help you.