Your Apps Know Where You Were Last Night, and They’re Not Keeping It Secret

At least 75 companies receive anonymous, precise location data from apps whose users enable location services to get local news and weather or other information. Several of those businesses claim to track up to 200 million mobile devices in the United States. The database reveals people’s travels in startling detail, accurate to within a few yards and in some cases updated more than 14,000 times a day. These companies sell, use or analyze the data to cater to advertisers, retail outlets and even hedge funds seeking insights into consumer behavior. It’s a hot market, with sales of location-targeted advertising reaching an estimated $21 billion. Businesses say their interest is in the patterns, not the identities, that the data reveals about consumers. They note that the information apps collect is tied not to someone’s name or phone number but to a unique ID. But those with access to the raw data — including employees or clients — could still identify a person without consent. They could follow someone they knew, by pinpointing a phone that regularly spent time at that person’s home address. Or, working in reverse, they could attach a name to an anonymous dot, by seeing where the device spent nights and using public records to figure out who lived there.


Your Apps Know Where You Were Last Night, and They’re Not Keeping It Secret