WuWeiAug 29, 2025
Electronic Frontier Foundation
At EFF we spend a lot of time thinking about the tech used by police and authorities to spy on you while you’re going about your everyday life, like cell-site simulators (CSS). Rayhunter is an open source tool we’ve created that we hope empowers everyone to help search out CSS around the world. https://www.eff.org/deeplinks/2025/03/meet-rayhunter-new-open-source-tool-eff-detect-cellular-spying
Meet Rayhunter: A New Open Source Tool from EFF to Detect Cellular Spying

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 cell-site simulators (CSS) around the world.

Electronic Frontier Foundation
Aug 26, 2025 at 10:58pmTypefully
Show threadKarl AuerbachAug 26, 2025

@eff It could be useful to pre-profile various locations where mobile CSS might be deployed in the future (such as near government buildings, on university campuses, etc) in order to construct baseline profiles of "normal".

Then we can develop a tool that looks at the baseline of an area and compare it with what is detected on the day of an event.

Entire cities could be baselined in this way by having people drive on patterns, collecting data, in order to map the baseline for an entire city.

(Back in the 1970's we did this kind of baselining, on foot, of parts of San Francisco, to make maps of land use etc.)

By-the-way, there is already legally data, such as maps showing the RF footprints of legitimate cell towers (and their directional radios) and data about call events.

Show threadBoltAug 26, 2025

@karlauerbach Could theoretically be useful, but I doubt it would do much to make detection any better.

Stingrays are pretty identifiable by their activity, since a lot of how they operate is made to cover the largest range of devices, meaning it will try many tactics at once (which are all visible), and will use tactics that aren't really something you could chalk up to just regular activity, since it's not commonly supported (e.g. requests to downgrade to 2G in a metropolitan area)

Show threadBoltAug 26, 2025
@karlauerbach I would still like to see something of the sort, though. I like those maps, but a lot of them could be better, and more data-complete.
Show threadKarl AuerbachAug 26, 2025
@boltx It could be useful to train an AI tool on "normal" activity patterns in an area so that "unusual" patterns could be fairly quickly noticed.
Show threadslashAug 26, 2025
@eff @janeishly I just got my Orbic in the mail. This weekend, it will become a Rayhunter. If I don't see anything interesting near me, I'll drive downtown to the Federal Building. I'd be surprised if they weren't running some Stingrays there. Definitely a must-have when I attend protests.
Show threadWilliam WhispersAug 27, 2025
@eff thanks for all works folks ! 🫡