At EFF we spend a lot of time thinking about Street Level Surveillance technologies—the technologies used by police and other authorities to spy on you while you are going about your everyday life—such as automated license plate readers, facial recognition, surveillance camera networks, and cell-site simulators (CSS). 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 CSS around the world.
CSS (also known as Stingrays or IMSI catchers) are devices that masquerade as legitimate cell-phone towers, tricking phones within a certain radius into connecting to the device rather than a tower.
CSS operate by conducting a general search of all cell phones within the device’s radius. Law enforcement use CSS to pinpoint the location of phones often with greater accuracy than other techniques such as cell site location information (CSLI) and without needing to involve the phone company at all. CSS can also log International Mobile Subscriber Identifiers (IMSI numbers) unique to each SIM card, or hardware serial numbers (IMEIs) of all of the mobile devices within a given area. Some CSS may have advanced features allowing law enforcement to intercept communications in some circumstances.
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Until now, to detect the presence of CSS, researchers and users have had to either rely on Android apps on rooted phones, or sophisticated and expensive software-defined radio rigs. Previous solutions have also focused on attacks on the legacy 2G cellular network, which is almost entirely shut down in the U.S. Seeking to learn from and improve on previous techniques for CSS detection we have developed a better, cheaper alternative that works natively on the modern 4G network.
To fill these gaps in our knowledge, we have created an open source project called Rayhunter.1 It is developed to run on an Orbic mobile hotspot (Amazon, Ebay) which is available for $20 or less at the time of this writing. We have tried to make Rayhunter as easy as possible to install and use, regardless of your level of technical knowledge. We hope that activists, journalists, and others will run these devices all over the world and help us collect data about the usage and capabilities of cell-site simulators (please see our legal disclaimer.)
Rayhunter works by intercepting, storing, and analyzing the control traffic (but not user traffic, such as web requests) between the mobile hotspot Rayhunter runs on and the cell tower to which it’s connected. Rayhunter analyzes the traffic in real-time and looks for suspicious events, which could include unusual requests like the base station (cell tower) trying to downgrade your connection to 2G which is vulnerable to further attacks, or the base station requesting your IMSI under suspicious circumstances.
Rayhunter notifies the user when something suspicious happens and makes it easy to access those logs for further review, allowing users to take appropriate action to protect themselves, such as turning off their phone and advising other people in the area to do the same. ...
