If you blink, you might miss the moment when he manages to steal valuable information without anyone noticing.

In the video below, Mark Rober urges viewers to be cautious of an emerging threat to their privacy. Using a deviously well-hidden device, Rober is able to steal the pin code of the woman in front of him at the grocery checkout without her — or anyone else around, for that matter — noticing what he had done.
The secret? A camera on his phone that is able to detect and record thermal images. A 2011 study published by the University of California, San Diego explores how effective these types of attacks are, and the results proved troubling. Luckily, Rober shares his advice on how to prevent these types of attacks below.