Researchers uncover new vulnerability for computers used in public places.

Security experts are discovering computers and smartphones being used in public places are vulnerable to hackers even if they are not connected to the Internet.

Low-power electronic signals that laptops emit could be read by spies or other eavesdroppers, researchers at the Georgia Institute of Technology have found.

"People are focused on security for the Internet and on the wireless communication side, but we are concerned with what can be learned from your computer without it intentionally sending anything," said Alenka Zajic, an assistant professor in Georgia Tech's school of electrical and computer engineering.

"Even if you have the Internet connection disabled, you are still emanating information that somebody could use to attack your computer or smartphone," he said in a statement. Because the spying is passive and emits no signals itself, users of computers and smartphones wouldn't know they're being watched.

By studying emissions from multiple computers, the researchers have developed a metric for measuring the strength of the leaks--known as "side-channel signals"--to help prioritize security efforts. The National Science Foundation and the Air Force office of scientific research are funding the research.

Side-channel emissions can be measured several feet away from an operating computer by using a variety of spying methods. For example, they can be received using antennas hidden in a briefcase.

Acoustic emissions--sounds produced by electronic components such as capacitors --can be picked up by microphones...