Clint Curtis, testified in front of the House Judiciary Committee in 2004 - he worked for Yang Enterprises, of whom Tom Feeney also worked while being a congressmen - Curtis was asked to design "vote flipping" software that was not detectable in the source code... here's a link to the video http://www.brasschecktv.com/page/465.html
Here's a video of how it works http://www.youtube.com/watch?v=1aBaX9GPSaQ (http://www.youtube.com/watch?v=1aBaX9GPSaQ)
Trust the machines. The machines are your friend. ???