Smartphones handle the jobs of many other objects: walkie-talkies, calculators, cameras. They pretend to be landlines and laptops and lightbulbs. They accomplish much of this multi-purposeness by tying into networks far vaster than any single device: into the GPS network, into the Internet, and into the cell network.
Many Americans don’t know that as they tote their phone around, some of those networks are watching. The cell network, specifically, creates a kind of record as a phone goes about its day. Every time a phone takes a call, exchanges a text, or uses an app to access the Internet, the cell provider takes notes, generating what’s called “cell site location information,” or CSLI. It records which cell tower was pinged by the phone, when that happened, and what direction its signal was coming from—and sometimes more information than that, too, depending on the newness of the phone and the tower.
Right now, in much of the U.S., law-enforcement agencies can access any CSLI from the past without getting a warrant. This is an extremely common practice: Between January and June 2015, Verizon said it received more than 20,000 of these police requests for location information nationwide. And in all of 2014, AT&T got more than 64,000 similar requests, or about 177 requests per day.