(1) Each time the player disconnects, save server info and time mark to the character. (2) Do that^ for every disconnection. (3) Each time the player joins a server, delete the disconnection data that is older than 10 minutes (ie. if that particular disconnection data is from over 10 minute ago). (4) Each time the player joins a server, compare disconnection entries to the current server. (5) If the player is found to be reconnecting to one of those servers within 10 minutes (see #3), auto-kick. Won't solve ALT+F4'ers but it will solve the server hopping to spawn behind somebody's back to kill him or her. Shouldn't be difficult, no?