Rayhunter: IMSI Catchers We Have Found So Far

Summary

A little over a year ago we released Rayhunter, our open source tool designed to detect cell-site simulators. We’ve been blown away by the level of community engagement on this project. It has been installed on thousands of devices (or so we estimate, we don’t actually know since Rayhunter doesn’t have any telemetry!). We have received dozens of packet captures, hundreds of improvements, both minor and major, documentation fixes, and bug reports from our open source community. This project is a testament to the power and impact of open source and community driven counter-surveillance. If this is your first time hearing about Rayhunter, you can read our announcement blog post here. Or if you prefer, you can watch our DEF CON talk. In short, Rayhunter is an open source Linux program that runs on a variety of mobile hotspots (dedicated devices that use a cellular connection to give you Wi-Fi). Rayhunter’s job is to look for cell-site simulators (CSS), a tool police use to locate or identify people's cell phones, also known as IMSI catchers or Stingrays. Rayhunter analyzes the “handshakes” between your Rayhunter device and the cell towers it is connected to for behaviors consistent with that of a CSS. When it finds potential evidence of a CSS it alerts the user with an indicator on the screen and potentially a push notification to their phone. Understanding if CSS are being used to spy on protests is one of the main goals of the Rayhunter project. Thanks to members of our community bringing Rayhunter to dozens of protests, we are starting to get a picture of how CSS are currently being used in the US. So far Rayhunter has not turned up any evidence of cell-site simulators being used to spy on protests in the US — though we have found them in use elsewhere. So far Rayhunter has not turned up any evidence of cell-site simulators being used to spy on protests in the US. There are a couple of caveats here. First, it’s often impossible to prove a negative. Maybe Rayhunter ju...