Link to Original Source
From TFA: The crack is a glorified guesser, and with the speed of modern PCs and the number of outstanding keys, the 25-digit serials are within range. The biggest problem for MS? If this gets widespread, and I hope it will, people will start activating legit keys that are owned by other people.
There is really no differentiating between a legit copy with a manually typed in wrong key and a hack attempt. Sure MS can throttle this by limiting key attempts to one a minute or so on new software, but the older variants are already burnt to disk. The cat is out of the bag. The crack was first mentioned on the Keznews forums, a step by step How-to can be found HERE"