“Many voting machines are running software that’s over a decade old, like Windows XP, which Microsoft hasn’t issued a security patch for since 2014. Others store ballots on memory cards, which could be used to insert viruses that can cause the machines to malfunction or alter votes. Take the Sequoia AVC Edge, for example, which is used in 12 states. It was hacked by a group of academics who installed malware that made the machine unable to do anything but play Pac-Man.
Still, there’s no indication that voting machines have ever been hacked in a U.S. presidential race before.”
Source: Here’s how hackers can wreak havoc on Election Day – Recode