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Cell Tracking

Can the government use your cell phone records to track your physical location without first obtaining a warrant based on probable cause? Often with EFF input as a friend of the court, the vast majority of judges issuing public opinions on the matter are saying “no”, and rejecting government applications for cell site location tracking information made without showing sufficient need for this kind of sensitive information. This issue came to light in August 2005, when the first judge to publish a decision on the issue—Magistrate Judge Orenstein in the Eastern District of New York—publicly denied a government request that lacked proof of probable cause. In doing so, Judge Orenstein revealed that the Justice Department had routinely been using a baseless legal argument to get secret authorizations from a number of courts, probably for many years. Many more public denials followed from other judges, sharply rebuking the government and characterizing its legal argument as as "contrived," "unsupported," "misleading," "perverse," and even a "Hail Mary" play. But the government continues to rely on the same argument in front of other judges, most often in secret and sometimes successfully. EFF has been asked to serve as a friend of the court in several of these applications, successfully showing judges how and why the government's arguments are baseless. EFF will continue to serve as a resource to courts and to counsel, to protect your privacy interest in your physical location, to stop the government from turning the cellular phone system into a vast network for warrantless physical surveillance and to ensure that Big Brother stays out of your pocket.

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EFF Related Content: Cell Tracking

Deeplinks Blog byCooper Quintin | September 10, 2025

Rayhunter: What We Have Found So Far

●Español Rayhunter is a program that runs on a variety of mobile hotspots and watches for cell-site simulators—a tool police use to locate or identify people's cell phones, also known as IMSI catchers or Stingrays. This project is a testament to the power and impact of open source and community driven... ●Read more about Rayhunter: What We Have Found So Far

Deeplinks Blog byAndrew Crocker | May 7, 2025

Appeals Court Sidesteps The Big Questions on Geofence Warrants

Another federal appeals court has ruled on controversial geofence warrants—sort of. The new opinion in Chatrie is a missed opportunity for the Fourth Circuit to join both other appellate courts to have considered the issue in finding geofence warrants unconstitutional. ●Read more about Appeals Court Sidesteps The Big Questions on Geofence Warrants

Deeplinks Blog byCooper Quintin, Will Greenberg | March 4, 2025

Meet Rayhunter: A New Open Source Tool from EFF to Detect Cellular Spying

●Español Rayhunter is a new open source tool we’ve created that runs off an affordable mobile hotspot that we hope empowers everyone, regardless of technical skill, to help search out cell-site simulators (CSS) around the world. ●Read more about Meet Rayhunter: A New Open Source Tool from EFF to Detect Cellular Spying

An animated image showing location pins dropping onto a street map from above, tracing several paths

Deeplinks Blog byAndrew Crocker | July 19, 2024

EFF Tells Minnesota Supreme Court to Strike Down Geofence Warrant As Fourth Circuit Court of Appeals Takes the Wrong Turn

We haven’t seen the end of invasive geofence warrants just yet, despite Google’s big announcement late last year that it was fundamentally changing how it collects location data. Today, EFF is filing an amicus brief in the Minnesota Supreme Court in State v. Contreras-Sanchez, involving a warrant... ●Read more about EFF Tells Minnesota Supreme Court to Strike Down Geofence Warrant As Fourth Circuit Court of Appeals Takes the Wrong Turn

Deeplinks Blog byBeryl Lipton, Cooper Quintin | June 12, 2024

The Next Generation of Cell-Site Simulators is Here. Here’s What We Know.

Dozens of policing agencies are currently using cell-site simulators (CSS) by Jacobs Technology and its Engineering Integration Group (EIG), according to newly-available documents on how that company provides CSS capabilities to local law enforcement. A proposal document from Jacobs Technology, provided to the Massachusetts State Police (MSP)... ●Read more about The Next Generation of Cell-Site Simulators is Here. Here’s What We Know.

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