The Open Voting Foundation has found yet more flaws in Diebold voting machines. A single switch on the motherboard allows someone to boot the machine from external memory. This would allow someone to change the way the machine counts votes. The machine can then be flipped back to the original memory, and no one would know the machine had been tampered with.
The flaw does require physical access to the machine, but many people have access to voting machine both before and after voting occurs. The Diebold machines do not provide an auditable paper trail of actual votes, which would allow an accurate after vote audit.
The tragedy here is that public officials have spent hundreds of millions of dollars of taxpayer money on defective machines that have to be replaced in order to be certain that our votes are being tallied properly.