  Accurate face recognition techniques make a series of critical applications
possible: policemen could employ it to retrieve criminals' faces from
surveillance video streams; cross boarder travelers could pass a face
authentication inspection line without the involvement of officers.
Nonetheless, when public security heavily relies on such intelligent systems,
the designers should deliberately consider the emerging attacks aiming at
misleading those systems employing face recognition.
  We propose a kind of brand new attack against face recognition systems, which
is realized by illuminating the subject using infrared according to the
adversarial examples worked out by our algorithm, thus face recognition systems
can be bypassed or misled while simultaneously the infrared perturbations
cannot be observed by raw eyes. Through launching this kind of attack, an
attacker not only can dodge surveillance cameras. More importantly, he can
impersonate his target victim and pass the face authentication system, if only
the victim's photo is acquired by the attacker. Again, the attack is totally
unobservable by nearby people, because not only the light is invisible, but
also the device we made to launch the attack is small enough. According to our
study on a large dataset, attackers have a very high success rate with a over
70\% success rate for finding such an adversarial example that can be
implemented by infrared. To the best of our knowledge, our work is the first
one to shed light on the severity of threat resulted from infrared adversarial
examples against face recognition.
