One that “can add, delete, or change votes on individual ballots.”
“… let me explain it for you. The ExpressVote XL, if hacked, can add, delete, or change votes on individual ballots — and no voting machine is immune from hacking … And let me explain some more: The ExpressVote XL, if adopted, will deteriorate our security and our ability to have confidence in our elections, and indeed it is a bad voting machine. And expensive, too!”
-Dr. Andrew Appel, Eugene Higgins Professor of Computer Science, Princeton University