[riri]

Seems like it would be easy enough to write into the code.

Though I wonder, how easy would it be for another programmer to spot this in the code? And I wonder how easy/possible would it be for the bad guys to code it to do this for a length of time and then revert back to the legitimate code.

All very distressing to think about.

[entropy12]

And I wonder how easy/possible would it be for the bad guys to code it to do this for a length of time and then revert back to the legitimate code.

You hit it the problem on the head. All it takes is a few seconds for the crooked technician manning the machines to insert a USB or similar portable memory device and change the code to normal right after voting closes. Which is why the best method is for the machine to eject a printed version of your vote on a paper ballot, and only those ballots are the official count. They are easy to scan since they are neatly printed by a machine and not hand marked.