Moscow, October 7 (RHC)-- Spy agencies in the United States and the United Kingdom have been aggressively developing tools to hack mobile phones without their owners' knowledge, according to U.S. intelligence whistleblower Edward Snowden.

Smart phone users can do "very little" to prevent spy agencies from getting "total control" over their devices, Snowden told the BBC's Panorama program from Moscow that was aired on Monday. The U.S. National security Agency (NSA) and its UK counterpart, Government Communications Headquarters (GCHQ), could gain access to a handset by sending it an encrypted text message.

Intelligence officials want to use the device to take photos or eavesdrop on citizens, Snowden said. "They want to own your phone instead of you.”

Ed Snowden is a U.S. privacy activist, computer professional, former CIA employee and former NSA contractor who leaked classified information about NSA spying programs in 2013. He leaked classified intelligence documents showing massive collections of phone records of Americans and foreign nationals as well as political leaders around the world.

Snowden, who lives in Russia where he has been granted asylum, has said that U.S. government surveillance methods far surpass those of an ‘Orwellian’ state, referring to George Orwell’s classic novel “1984,” which describes a society where personal privacy is continuously invaded by spy agencies.

The NSA whistleblower also told the BBC that he has offered to return to the United States and go to prison. Snowden said he and his lawyers were waiting for U.S. officials "to call us back." He said that "so far they've said they won't torture me, which is a start, I think. But we haven't gotten much further than that."