  When users leave their mobile devices unattended, or let others use them
momentarily, they are susceptible to privacy breaches. Existing technological
defenses, such as unlock authentication or account switching, have proven to be
unpopular. We conducted interviews to uncover practices users currently engage
in to cope with the threat, and found that it is common for users to try to
keep their devices under close supervision at all times. One obstacle to this
strategy is that displaying such protective behavior can be detrimental to
social relationships. To address these concerns, we built a software tool that
gathers activity logs in the background. Logs can later be reviewed as a
timeline of opened apps and the actions performed within each, with events
decorated with pictures captured inconspicuously with the front-facing camera.
We evaluated this approach in a user study, and found participants to be
generally eager to adopt the technology, although in different ways. Most users
foresaw using it as a deterrent, or to check if they were snooped on, if that
suspicion were ever to arise. Yet, some voiced the intention of creating "honey
traps". The results highlight both the opportunities and the potential dangers
of the logging approach.
