There are two types of shoulder-surfing attack: direct observation attacks, in which authentication information is obtained by a person who is directly monitoring the authentication sequence, and recording attacks, in which the authentication information is obtained by recording the authentication sequence for later analysis to open the device. Apart from threats to password or PIN entry, shoulder surfing also occurs in daily situations to uncover private content on handheld mobile devices; shoulder surfing visual content was found to leak sensitive information of the user and even private information about third-parties.
