In George Orwell’s novel “1984,” Big Brother watches citizens through two-way, TV-like telescreens to surveil citizens without any cameras. In a similar fashion, our current smart devices contain ambient light sensors, which open the door to a different threat: hackers. These passive, seemingly innocuous smartphone components receive light from the environment and adjust the screen's brightness accordingly, like when your phone automatically dims in a bright room. Unlike cameras, though, apps ar...