Susan Pynchon, a member of Florida Coalition for Fair Elections, has a very powerful piece on CounterPunch.org, where she describes witnessing the Harri Hursti Hack, when he proved to Ion Sancho (The Leon County Supervisor of Elections) that the Diebold machines in use could be hacked.
A snippet:
“It was a powerful moment and, I will admit, it had the unexpected result for me personally of causing me to break down and cry. Why did I cry? It was the last thing I thought I would do, but it happened for so many reasons. I cried because it was so clear that Diebold had been lying. I cried because there was proof, before my very eyes, that these machines were every bit as bad as we all had feared. I cried because we have been so unjustly attacked as “conspiracy theorists” and “technophobes” when Diebold knew full well that its voting system could alter election results. More than that, that Diebold planned to have a voting system that could alter results. And I cried because it suddenly hit me, like a Mack truck, that this was proof positive that our democracy is and has been, as we have all feared, truly at the mercy of unscrupulous vendors who are producing electronic voting machines that can change election results without detection.”
The piece goes through the whole process in detail. The voting system must be open sourced and verified by the security community before it can be used. It is also probable that a paper ballot will always be needed as a check mechanism.