The newly released Mac App Store, which is a iOS-like app store but for use on the Mac has already been hacked. A user “Anonymous” has posted on the popular PasteBin a procedure on how to trick Applications such as Angry Birds, to think it’s been purchased through the Mac App Store.
The files “_CodeSignature, _MASReceipt and CodeResources” are imbedded into the applications package file when purchased, however, you can easily access these files using the “Show Package Contents” option. Simply copying these files from a free app you have purchased and then downloading the app you want to use and pasting the files into it, tricks it.
More information on can be found here: http://pastebin.com/1eWf9LCg