NSA whistle-blower Edward Snowden and hardware hacker Andrew Huang have designed a device which detects whether or not a phone's radio is transmitting. This is to combat the ability of government agencies to turn a person's own phone into a tool of surveillance. While anyone concerned about government surveillance could make use of such a device, Snowden considers journalists to be in particular need of such protection. "One good journalist in the right place at the right time can change history," Snowden said during an MIT Media Lab video stream, "This makes them a target, and increasingly tools of their trade are being used against them."
Phones normally include an airplane mode to turn off the radio, but, in the paper describing the device, the pair warn that airplane mode is not safe. The GPS is still active in airplane mode on iPhones with iOS versions 8.2 and later. Even on other devices, airplane mode may still not be completely trustworthy. Phones infected by malware can have their radios turned on without giving any indication in the user interface. As the paper states, "trusting a phone that has been hacked to go into airplane mode is like trusting a drunk person to judge if they are sober enough to drive." Trying to turn off a phone offers no more protection than airplane mode, because some malware is capable of making a phone appear turned off when it isn't
The paper describes the design of a device they call the introspection engine. It works by snaking wires into the phone and through the SIM card slot, and attaching to the phone's circuit board. Once attached the introspection engine can detect signals sent by the phone's antenna. Since this solution is very dependent on a phone's specific hardware, they chose to start by focusing on one particular phone model. The introspection engine described in the paper works with the iPhone 6 because they believe it is the most common phone used by reporters. However, given enough time, it should be possible to design similar devices to work with other phone models.
The pair intends to spend the next year testing the capabilities of the introspection engine. If the prototype performs to their expectations they intend to seek funding to develop a supply chain to so they can provide journalists with modified iPhone 6 devices. The supply chain would be based in China, which may cause concern for some who might otherwise consider using the devices. However, Huang states that the device's hardware and software specifications will be open-source, which he believes should alleviate any concerns about the trustworthiness of Chinese manufacturers.