In 2006, Princeton computer science professor Edward Felten received an anonymous message offering him a Diebold AccuVote TS, one of the most widely used touch-screen voting machines at the time. Felten's team then spent the summer working ... to reverse-engineer the machine. In September 2006, they published a research paper and an accompanying video detailing how they could spread malicious code to the AccuVote TS to change the record of the votes to produce whatever outcome the code writers desired. And the code could spread from one machine to another like a virus. That was more than a decade ago, but Georgia still uses the AccuVote TS. The state is one of five ― the others are Delaware, Louisiana, New Jersey and South Carolina ― that rely entirely on [direct-recording electronic machines, or] DREs for voting. Ten other states use a combination of paper ballots and DRE machines that leave no paper trail. Many use a newer version of the AccuVote known as the TSX ― even though computer scientists have demonstrated that machine, too, is vulnerable to hacking. Others use the Sequoia AVC Advantage, which Princeton professor Andrew Appel demonstrated could be similarly manipulated in a 2007 legal filing. On Nov. 7, the day before last year's elections, former CIA Director James Woolsey flagged DRE voting machines as a key vulnerability. "If I were a bad guy from another country who wanted to disrupt the American system ... I'd concentrate on messing up the touch-screen systems," he told Fox News.