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Researchers at the University of Washington are developing tech to detect the use of a controversial device used by law enforcement to track and surveil cellphones.

Recently, the researchers conducted tests in Seattle and Milwaukee over a two-month period, paying rideshare service drivers $25 a week to haul around a device which may detect cell-site simulators.


Law enforcement agencies from the FBI to state and local police departments use cell-site simulators‚ÄĒalso known as ‚ÄúStingrays‚ÄĚ after the popular model‚ÄĒto track suspects and determine their location. These devices connect to nearby cellphones by masquerading as legitimate cell towers; this allows police to approximate the location of a target‚Äôs cellphone.

Typically, the Stingrays used by police only capture metadata (data on who placed a call, when, and where) though some cell-site simulators are capable of intercepting content‚ÄĒmeaning actual conversations and texts.


Stingrays are considered controversial because they tend to be very disruptive when deployed in busy areas. It is, by definition, a cellphone jammer: During use, the device is known to prevent bystanders from placing calls, even to emergency services like 911. The feds are also very secretive about Stingrays, going so far as to forcibly remove records from local agencies to prevent disclosure under public records law.

Last month, the feds reportedly deployed a Stingray to track an undocumented immigrant in Detroit‚ÄĒa sign the technology may be deployed more regularly under the new administration.


The Stingray-detection device built by the Washington researchers, called SeaGlass, is roughly the size of a suitcase. It contains a Raspberry Pi, a cellular hotspot, GPS module, and GSM cellular modem, along with an Android phone running SnoopSnitch, an app that collects data on nearby cell towers. The device was placed in the back of 15 ridesharing vehicles, nine in Seattle and six in Milwaukee.

While there’s no conclusive evidence as of yet that SeaGlass is effective, the researchers believe they may have detected at least two Stingray devices in use, the first near SeaTac airport and the other near the Seattle offices of the US Customs and Immigration Service (ICE). A third possible detection occurred in a Seattle neighborhood, though the data was less convincing.


The Seattle police and Port of Seattle police both told Wired they didn‚Äôt own Stingrays. The FBI meanwhile declined to comment‚ÄĒno surprise there‚ÄĒand ICE provided a boilerplate response: ‚ÄúCell-site simulators are invaluable law enforcement tools that locate or identify mobile devices during active criminal investigations.‚ÄĚ

Since the FBI requires local police departments to sign non-disclosure agreements before authorizing their use, it’s unlikely the Bureau will be thrilled when average citizens begin tracking their use.