A geofence search warrant (also known as a geofence warrant) is a search warrant issued by a court that allows law enforcement to search a database to find all active mobile devices within a specified geofence area. Courts have issued geofence search warrants to law enforcement agencies to obtain information from databases such as Google’s Sensorvault, which collects users’ historical geo-location data via GPS records.
A geofence search warrant does not work for future geo-location data, nor does it work for real-time geo-location data.
Shortly before 5 p.m. on May 20, 2019, an armed man entered a bank in Midlothian, Virginia, forced an employee to open a safe and fled with $195,000. Security footage showed the man holding a cellphone to his ear just before the robbery – a detail that prompted police to try a surveillance technique that is becoming increasingly popular with U.S. law enforcement.
When authorities had not yet identified the suspect several weeks after the robbery, an officer obtained a search warrant for the Google location data of all cell phones that had been near the Call Federal Credit Union bank during the robbery. From a list of 19 accounts, investigators were able to narrow their search to a 24-year-old Richmond man named Okello Chatrie, whom they eventually charged with armed robbery.
The demand for Google data, known as a geofence warrant, is a way for law enforcement to leverage the company’s collection of massive amounts of information about its customers. The warrants allow police to track just about anyone who uses an Android device or a company app – such as Google Maps or Gmail – to a specific location over a period of time. As more police use such warrants, the method is raising concerns among privacy advocates, who say the government is collecting information from people in violation of the Fourth Amendment, which protects against unreasonable searches.
Based on real-life stories like the one above, Android users think that removing Google components from their Android phones will make those phones “invisible” to Google. And thus invisible to law enforcement. A very wrong conclusion.
Here’s why: Geofence warrants are usually not issued for Google location data (only) for one simple reason: not everyone uses an Android phone. If this is the case, a robber using a dumb phone or an iPhone will easily escape, which is not the case.
Police use what they call a “cell dump“. A “cell dump” is the sharing of identifying information by a cell tower operator that can be used to identify where a particular person was at a particular time. When cell phone users move, their devices connect to nearby cell towers to maintain a strong signal even when the phone is not actively in use. In this way, law enforcement has access to the geolocation of every cell phone, not just the geolocation of Android phones.
And yes, de-geolocated Android smartphones are susceptible to cell dump techniques, just like any other phone. There is no difference and no real privacy, not to mention security.