What anti-cheat protection does MW3 have?

MW3 will again be using Valve's anti-cheat system VAC.

The inclusion of dedicated servers in MW3 should allow for a better implementation than was done for MW2. VAC is designed to use a delayed banning system so that cheaters can't tell which cheat caused them to be banned. Due to this it is expected to be used in addition to server administrators to kick/ban cheating users from their server till that point. I can't seem to find much details on the abilities of server admins or if kick voting will be available though.

It won't require any additional middleware software except for Steam which is required to run the game.

VAC itself doesn't have an official publicly searchable database but using the Steam Community you can see the VAC status of anyone with a public profile. I you want a searchable list of banned players you can use VAC Banned its an unofficial database of people who have been banned by VAC.

For consoles, Activision has bans of different types for boosting, cheating, glitching, hacking, offensive behavior, and offensive gamertag. It isn't clear exactly how they detect such offenses, but there is a reddit site for reporting if you are interested. I'd probably not go to the trouble, but I'm glad there are people that do.