Ambient light sensors are categorized as low-risk by device makers and can often be accessed directly by software (or malware) without any permissions or privileges. Nevertheless, previous studies have shown such a rudimentary sensor can provide enough information to infer keystrokes on a virtual keyboard and steal a device PIN, about 80% of the time. The new research shows what an ambient light sensor can do when combined with an active light source component – namely the device' screen.