Leaver Buster

Leaver Buster is an automated system that Riot implemented to discourage players from leaving League of Legends matches.
 * Leaving the game during champion selection.
 * Punishment: 1st offence - 6 minutes prohibited from joining the queue. 2nd offence - 15 minutes prohibited from joining the queue. 3rd offense - 1 hour prohibited from joining the queue. The counter resets after 8 hours.
 * If the game was a ranked match, his Elo will be reduced accordingly.
 * Leaving the game before the match is over
 * Punishment: no XP/IP granted for the game the player left and a leave added to his profile.

If a game doesn't end (for example for server issues, or because every player left the match), no penalties are given out.

After receiving a certain number of leaves, which varies depending on the total number of games played and the distance in time between each leave, the player account gets first warned and then suspended for increasingly long periods of time, resulting in a permanent ban for re-iterated offenses.