SurveillanceBringing transparency to cell phone surveillance

Modern cell phones are vulnerable to attacks from rogue cellular transmitters called IMSI-catchers — surveillance devices that can precisely locate mobile phones, eavesdrop on conversations or send spam.

Recent leaks and public records requests have revealed that law enforcement in many U.S. cities have used the surveillance devices to locate suspects or hunt for illegal activity. But despite extensive public debate about their use and privacy implications, little is known about how comprehensively International Mobile Subscriber Identity- (IMSI) catchers — also known as cell-site simulators or Stingrays — are being used by governments, hackers or criminals in any given city.

UW says that University of Washington security researchers have developed a new system called SeaGlassto detect anomalies in the cellular landscape that can indicate where and when these surveillance devices are being used. The new system is described in a paper to be published in June 2017 in Proceedings on Privacy Enhancing Technologies.

“Up until now the use of IMSI-catchers around the world has been shrouded in mystery, and this lack of concrete information is a barrier to informed public discussion,” said co-lead authorPeter Ney, a doctoral student at the Allen School of Computer Science & Engineering at the UW. “Having additional, independent and credible sources of information on cell-site simulators is critical to understanding how — and how responsibly — they are being used.”

During a two-month deployment in which SeaGlass sensors were installed in fifteen ridesharing vehicles in Seattle and Milwaukee, researchers identified dozens of anomalies that were consistent with patterns one might expect from cell-site simulators.

However, researchers cautioned, without corroborating evidence from public records requests or other documentation about where cell-site simulators are being used — or suspicious activity seen over a longer period of time — they cannot definitively say the signals came from IMSI-catchers.

“In this space there’s a lot of speculation, so we want to be careful about our conclusions. We did find weird and interesting patterns at certain locations that match what we would expect to see from a cell-site simulator, but that’s as much as we can say from an initial pilot study,” co-lead author Ian Smith, a former Allen School research scientist. “But we think that SeaGlass is a promising technology that — with wider deployment — can be used to help empower citizens and communities to monitor this type of surveillance.”

Cell-site simulators work by pretending to be a legitimate