With Diebold voting machines, every vote is stored on a memory card along with additional computer code.  This video clip from the HBO special “Hacking Democracy” shows how an election can be altered through a person only having access to a memory card.  The video shows how the hack works even with Diebold machines that only tabulate paper ballots, and how it is impossible to detect the fraud once it has happened.

This video is part of the article A Summary of Election Fraud Issues in the United States.