New FBI Documents Shed More Light on Cell Phone Location Tracking Capabilities

Posted on December 13, 2021

A recent article by Motherboard paints the clearest picture yet on how the nation’s top law enforcement body queries Americans’ cellular location data. The centerpiece of the story, a training document produced by the FBI’s Cellular Analysis Survey Team (CAST), was obtained via a FOIA request submitted by Property of the People, a nonprofit group dedicated to leveraging public records laws to pry loose government documents.

The 2019 slide deck depicts an FBI unit that serves as a mobile location data clearing house for the bureau as well as its state and local partner law enforcement agencies. Essentially, CAST provides telecom data analysis, cellular network coverage testing, guidance and testimony by subject matter experts, and even a location data visualization tool known as “CASTViz” to law enforcement across the country.

The Motherboard piece explores CASTViz in particular and very much deserved detail. As is common with public scrutiny of formerly undisclosed government documents, even mundane passages can be illuminating. One of the article’s quotes from the primary source material serves as a good example: “CASTViz has the ability to quickly plot call detail records and tower data for lead generation and investigative purposes.” This reinforces what civil liberties defenders have long warned about: that the FBI is reviewing location data not merely as the object of a valid search warrant, such as to locate a suspect for whom the bureau has probable cause to believe committed a violent crime. Rather, the FBI goes much further, making a practice of trawling location data for “lead generation”, long before the probable cause investigatory threshold can be established. This makes it comparatively easy for the FBI to get its hands on the location data of any mobile device user on US soil, even if the pursuit of a lead reaches a dead end.

The newly released training document also delineates the data retention schedules for major mobile telecoms, information which these companies don’t exactly state forthrightly. Although retention varies by data type, most cellular network providers keep most data for at least one year, with AT&T keeping much of theirs for as long as seven years. All of these details taken together, any agents or other law enforcement personnel party to this training resource enjoy a clear picture of exactly what data they can query from which telecoms, and how.

It should come as no surprise that law enforcement is constantly advancing and refining its tradecraft. But the fact that this robust suite of location data capabilities rests in the hands of an agency with a long history of treating protected First Amendment activity as meriting criminal investigation is where civil liberties advocates are rightly concerned. This document serves as a modest start in cataloging law enforcement’s spying powers so that they can be properly constrained to protect Americans’ constitutional freedoms.

You can read the full piece from Motherboard, including excerpts of the referenced FBI document, here.