“A simply anonymized dataset does not contain name, home address, phone number or other obvious identifier,” they wrote. “Yet, if individual’s patterns are unique enough, outside information can be used to link the data back to an individual.”
tracked by their mobile carrier’s cell towers, four “data points” were all they needed to figure out the person’s identity 95% of the time.
So, for example, say that you wake up at home every morning, head to the office five days a week, then hit the gym on three of those days. That’s three data points already. Then maybe you go to the same church, or restaurant for brunch, every Sunday. There’s the fourth — plenty to figure out who you are, the authors say.
Every additional location you hit regularly just makes it that much easier.