What exactly does a pacemaker do?A pacemaker is an electrical device that helps control irregular heartbeats using electrical pulses. They are about the size of a pocket watch, and are placed under the skin near the heart.And they are easily hacked? Well, not easily. But it's "100 percent possible," says Barnaby Jack, Director of Security Research for a security company called IO Active. At a recent conference, Jack used a laptop to hack into a remote pacemaker, and reverse-engineered it to send a series of deadly 830-volt shocks. Jack then took the demonstration one step further, accessing the device's model and serial number, as well as usernames and passwords for the manufacturer's development servers. Using this information, he says it would be very easy to load a virus that could spread between numerous pacemakers, giving a malevolent hacker the ability to commit mass murder.