People share a lot of their life on Facebook, but they probably don’t know the extent of the intimate details their use of the site reveals about themselves. That’s why Danish coder Søren Louv-Jansen built a simple program that allowed him to create sleep schedules for all of his friends based on when they were last active on Facebook.
Facebook sends that “last active” information to your browser in plain text, where it is available and visible to all of your friends. Louv-Jansen simply built a program that recorded those timestamps every ten minutes, creating an accurate picture of when his friends first checked Facebook in the morning and last checked at night.
“Everybody I’ve shown this have been equally fascinated and outraged by the accuracy with which it predicts their sleep patterns. In this digital world we leave footprints everywhere we go, and when we do it, without even thinking about it,” he said. “Facebook might block this little ‘hack’, so your friends no longer can track you, but Facebook will always be able to do their own data analysis which is undoubtedly way better than what I’ve come up with.”
Without even knowing it, Facebook users can expose details of their private lives just by logging in.