A mockup of Edward Snowden and Bunnie Huang's iPhone modification, showing the SIM card slot through which their hardware add-on would access the phone's antennae to monitor them for errant signals. Andrew Huang & Edward Snowden

When Edward Snowden met with reporters in a Hong Kong hotel room to spill the NSA's secrets, he famously asked them put their phones in the fridge to block any radio signals that might be used to silently activate the devices' microphones or cameras. So it's fitting that three years later, he's returned to that smartphone radio surveillance problem. Now Snowden's attempting to build a solution that's far more compact than a hotel mini-bar.

On Thursday at the MIT Media Lab, Snowden and well-known hardware hacker Andrew "Bunnie" Huang plan to present designs for a case-like device that wires into your iPhone's guts to monitor the electrical signals sent to its internal antennas. The aim of that add-on, Huang and Snowden say, is to offer a constant check on whether your phone's radios are transmitting. They say it's an infinitely more trustworthy method of knowing your phone's radios are off than "airplane mode," which people have shown can be hacked and spoofed. Snowden and Huang are hoping to offer strong privacy guarantees to smartphone owners who need to shield their phones from government-funded adversaries with advanced hacking and surveillance capabilities—particularly reporters trying to carry their devices into hostile foreign countries without constantly revealing their locations.

"One good journalist in the right place at the right time can change history," Snowden told the MIT Media Lab crowd via video stream. "This makes them a target, and increasingly tools of their trade are being used against them."1

"They're overseas, in Syria or Iraq, and those [governments] have exploits that cause their phones to do things they don't expect them to do," Huang elaborated to WIRED in an interview ahead of the MIT presentation. "You can think your phone's radios are off, and not telling your location to anyone, but actually still be at risk."