it isn't acctually a hack because it is an inherent flaw designed inside each of these games which could easily be corrected if the weapon limitations where designed correctly. they are exploiting this flaw... but because it is an exploit, all players have access to it.
all controllers are capable of this 'rapid fire' capability and one can do it by not even really modding a controller, but learning how to do it...
the flaw is semi-automatic weapons are not limited in their rate of fire.
unlike automatic weapons which says specifically that the weapon has a RoF of 600 or 900, and no matter how frequently you pull the trigger you'll never exceed these limitations, pistols and other semi autos in game lack a RoF limitation. it will fire of how ever fast you can pull the trigger. if you can pull the trigger at 2000 times per minute, the weapon will fire at 2000 rounds per minute... and this isn't acctually humanly impossible, because you are pressing the trigger at 33 times a second. well with in the limitations of both the controller and your body if using certian methods, and quiet a few people can achieve that for a few seconds... example Metal Gear Solid torture scene, keeping snake at full health...
they are not cheating.
they are not hacking.
they are using a mechanic which exists in game to their advantage.
and weither or not this is exploiting is arguable really.
if it was an unintended flaw, then they should of corrected it long ago. this problem still exists in games like Counter Strike, Call of Duty 4, half life 2, and damn near every other FPS with a pea shooter pistol.