Robert Bowling goes into detail of every possible ban that Modern Warfare 3 players might receive for various offenses. With the recent bans going out to prestige token exploiters, Bowling has listed on the official forums what every offence entails.

Boosting

Any player demonstrating ‘game abuse’ in the form of organizing cooperative or single game play for the purpose of gaining experience, prestige, score, weapon levels, icons, titles or other related in-game unlocks.
( i ) First Offense: With proper verification, user is banned for 48 hours and a stats reset.
(ii) Second Offense: With proper verification, user is banned for 48 hours and a stats reset, and a permanent ban from leaderboards.
(iii) Third Offense: With proper verification, user is banned for 7 days and a stats reset, and a permanent ban from leaderboards.

Cheating 

Any player demonstrating ‘game abuse’ in the form of unknown boosting, glitching, hacking or other related offenses for the purpose of gaining experience, prestige, score, weapon levels, icons, titles or other related in-game unlocks.
( i ) First Offense: With proper verification, user is banned for 48 hours and a stats reset.
(ii) Second Offense: With proper verification, user is banned for 48 hours and a stats reset, and a permanent ban from leaderboards.
(iii) Third Offense: With proper verification, user is banned for 7 days and a stats reset, and a permanent ban from leaderboards.

Glitching

Any player demonstrating ‘game abuse’ in the form of organizing cooperative or single game play for the purpose of gaining experience, prestige, score, weapon levels, icons, titles or other related in-game unlocks. Examples: Exploiting map holes, the javelin glitch, and participating in modded lobbies
( i ) First Offense: With proper verification, user is banned for 48 hours and a stats reset.
(ii) Second Offense: With proper verification, user is banned for 48 hours and a stats reset, and a permanent ban from leaderboards.
(iii) Third Offense: With proper verification, user is banned for 7 days and a stats reset, and a permanent ban from leaderboards.

Hacking

Any player demonstrating ‘game abuse’ in the form of modifying the executable or creating infected lobbies with or without the purpose of gaining experience, prestige, score, weapon levels, icons, titles or other related in-game unlocks.
( i ) First Offense:  With proper verification, user is console banned.

Offensive Behavior

Any player demonstrating in-game verbal abuse, harassing, or other related behavior deemed as universally unacceptable to other players.
( i ) First Offense: With proper verification, user is banned for 24 hours

Offensive Gamertag

Any player demonstrating an offensive in-game gamer tag, to be decided as universally unacceptable to other players.
( i ) First Offense:  With proper verification, user is reputation banned 5000. A reputation ban that exceeds a certain threshold can lead to bans from playing.