To be fair, a phone that is fully switched off can’t do a thing. But what if you only thought you had turned it off?
Back in 2006, media reported that the FBI applied a technique known as a “roving bug” which allowed them to remotely activate a cell phone’s microphone and listen to nearby conversations.
Pinpointing a person’s location to within just a few meters has not been a problem either thanks to a tracking device built into mobile phones.
…In July last year, Washington Post wrote that “By September 2004, a new NSA technique enabled the agency to find cellphones even when they were turned off.”
…if an attacker had a chance to install malware before the phone is turned off, the software could make it only look like the phone is shutting down. Instead, it “enters a low-power mode that leaves its baseband chip—which controls communication with the carrier—on”.
Such “playing dead” state would allow the phone to receive commands, including one to activate its microphone.
Source: RT.com
So, just like in the movies, what you need to do is remove the battery.
If that is impossible because you have an iPhone, you can do this:
- hold the home and power buttons simultaneously for 10 seconds . This will put the phone in too low level a state for anything to able to interact with its baseband
- the phone won’t turn on when someone holds the power button or power up when the phone is plugged into a power source
- to use the phone again, hold the power button and home button together until the Apple logo appears
