Report : For the study , the research team studied 15 months of anonymous mobile data for roughly 1.5 million people . It 's easy to identify smartphone users by their movements . Researchers from MIT and elsewhere tracked 1.5 million people for two years . Each mobile user 's daily movements are unique and create a ` ` . '' Some advocates worry how law enforcement and others may use that data .
Report : It 's easy to identify smartphone users by their movements . Researchers from MIT and elsewhere tracked 1.5 million people for two years . Each mobile user 's daily movements are unique and create a ` ` . '' Some advocates worry how law enforcement and others may use that data .