The Private Match Hack allows players to create their own private match in which they can gain double experience from. The most disruptive part of this glitch is the fact that it takes players out of the games they selected, and instead drops them into a game not of their choice. Additionally, as the bug heavily involves the use of friends lists and the Xbox Live interface it can only be done on the Xbox 360 version of Modern Warfare 2.
This glitch also allows you to kill players on the same team and have their death count towards your overall score. This also effects killstreaks, which can then be used to kill more team members . Robert Bowling Community Manager for Infinity Ward has posted up on Twitter that they are aware of the issue, and are currently looking into the exploit.