radio waves
Computers housing the world's most sensitive data are usually "air-gapped" or isolated from the internet. They're also not connected to other systems that are internet-connected, and their Bluetooth feature is disabled, too. Sometimes, workers are not even allowed to bring mobile phones within range of the computers. All of this is done to keep important data out of the hands of remote hackers.

But these security measures may be futile in the face of a new technique researchers in Israel have developed for stealthily extracting sensitive data from isolated machines - using radio frequency signals and a mobile phone.

The attack recalls a method the NSA has been secretly using for at least six years to siphon data in a similar manner. An NSA catalogue of spy tools leaked online last year describes systems that use radio frequency signals to remotely siphon data from air-gapped machines using transceivers - a combination receiver and transmitter - attached to or embedded in the computer instead of a mobile phone. The spy agency has reportedly used the method in China, Russia and even Iran. But the exact technique for doing this has never been revealed.

The researchers in Israel make no claims that theirs is the method used by the NSA, but Dudu Mimran, chief technology officer at the Israeli lab behind the research, acknowledges that if student researchers have discovered a method for using radio signals to extract data from hard-to-reach systems, professionals with more experience and resources likely have discovered it, too.

Read more on Wired.com.