According to this site (http://gizmodo.com/gadgets/gadgets/how-to-steal-an-election-with-a-diebold-machine-200693.php), this “hack” will allow a user to load their own software into the machine. My guess is that the switch tells the MB to load software from whatever’s in the USB port.
Correct.
This was demonstrated a long time ago (at least a year) as a way to install replacement system and/or application software into the voting machine. It's essentially a functional takeover of the box, as far as I can tell.
Obviously, a Flash drive with pictures of your Aunt Susie at Niagara Falls is not going to do the trick -- you have to put a reasonable image of the desired (hacked) system software on the Flash drive, meaning you have to be a pretty high-level hacker to start with.
OK, that’s different than what I remember from a year or so ago. That’s actually worse than that exploit.
Ooops.