Computers housing the world’s most sensitive data are usually 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.