
“The 2010 discovery of the Stuxnet cyberweapon, which used a thumb drive to attack Iran’s nuclear facilities and spread among its computers, illustrated how one type of attack could work. Most at risk are paperless e-voting machines, which don’t print out any record of votes, meaning the electronically stored results could be altered without anyone knowing they had been changed. In a tight election, the result could be the difference between winning and losing. A Monitor analysis shows that four swing states – Pennsylvania, Virginia, Colorado, and Florida – rely to varying degrees on paperless machines.”
http://www.csmonitor.com/layout/set/print/USA/Elections/2012/1026/Could-e-voting-machines-in-Election-2012-be-hacked-Yes