Individuals can be uniquely identified with just four points of location data, a study of mobile phone records shows.
Countless mobile applications make use of location data, and such information is increasingly used to tailor both services for users and advertisements.
But a study in Scientific Reports warns that human mobility patterns are unique identifiers, even when data are scarce.
It presents a formula to describe the trade-off between genuine anonymity and the "resolution" of location data.
The growing ubiquity of mobile phones and smartphone applications has ushered in an era in which tremendous amounts of user data have become available to the companies that operate and distribute them - sometimes released publicly as "anonymised" or aggregated data sets.