Better the devil you know:using lost-smartphone scenarios to explore user perceptions of unauthorised access

Smartphones are a central part of modern life and contain vast amounts of personal and professional data as well as access to sensitive features such as banking and financial apps. As such protecting our smartphones from unauthorised access is of great importance, and users prioritise this over protecting their devices against digital security threats. Previous research has explored user experiences of unauthorised access to their smartphone - though the vast majority of these cases involve an attacker who is known to the user and knows an unlock code for the device. We presented 374 participants with a scenario concerning the loss of their smartphone in a public place. Participants were allocated to one of 3 scenario groups where a different unknown individual with malicious intentions finds the device and attempts to gain access to its contents. After exposure, we ask participants to envision a case where someone they know has a similar opportunity to attempt to gain access to their smartphone. We compare these instances with respect to differences in the motivations of the attacker, their skills and their knowledge of the user. We find that participants underestimate how commonly people who know them may be able to guess their PIN and overestimate the extent to which smartphones can be g'hacked into'. We discuss how concerns over the severity of an attack may cloud perceptions of its likelihood of success, potentially leading users to underestimate the likelihood of unauthorised access occurring from known attackers who can utilize personal knowledge to guess unlock codes.