Computer security experts have warned for years that some voting machines are vulnerable to attack. And this week, in Virginia, the state Board of Elections decided to impose an immediate ban on touchscreen voting machines used in 20 percent of the state's precincts, because of newly discovered security concerns. The problems emerged on Election Day last November. "One machine would go and crash. They'd bring it back up. Another one would crash," said Edgardo Cortes, the state's elections commissioner. State auditors investigated. While using their smartphones, they were able to connect to the voting machines' wireless network, which is used to tally votes. Investigators easily guessed the system's passwords - in one case, it was "abcde" - and were then able to change the vote counts remotely without detection. Jeremy Epstein is co-founder of Virginia Verified Voting and one of many computer experts who had warned about the security flaws. He's not at all surprised by the state's findings. Epstein said the vulnerabilities could be used to create a lot of mischief, "to change the list of races, change the list of candidates, change the votes that have been recorded, change the totals recorded, things like that."