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by pacificresearch 1530 days ago
Hi, author here. If you have any questions about IMSI catchers I'd be happy to help :)
3 comments

Hi, this sounds interesting... But when I try to enter the site I just get a image of an armadillo. I do browse with javascript disabled so that is most likely the reason, but I can also imagine that a fair bit of your audience are among the slightly more paranoid end so if you want to reach out I would recommend you to make a page that can be viewed without requiring javascript.
This is a fair criticism and something I'll bring up with the team
Do you plan to upload your kernel sources? This site seems ambiguous considering the open source nature of the product...
Yes, although the code needs to be updated you can view our kernel code here : https://github.com/pacificresearchalliance/kernel_google_cro...

The only changes to the kernel required for our Radio Sentinel app are DIAG_CHAR=y when building.

Crosshatch is the pixel 3xl which is EOL. Any sources for your devices in stock?
Thanks for the article!

Can you explain, how an IMSI catcher works on a protocol level?

There's a wide variety of attack methods, however most usually fall into one 1 of 2 types:

1. Active interception. The IMSI catcher is actively transmitting data to the victim device and forcing it to connect, appearing to be a normal cell tower. These are the most common and can usually get a very accurate location. Because 4G and earlier don't require the tower to authenticate to the device, only the device to the tower, there really isn't any vulnerability required to do this. They use different tricks to entice the victim to connect or update its location ( e.g: falsely inflating it's signal strength, appearing to be the only tower in a location, increasing the frequency of location updates ) . Some of these techniques are mentioned in the "Warnings" section of another article describing our Radio Sentinel app: https://armadillophone.com/blog/radio-sentinel

2. Passive interception. The IMSI catcher doesn't transmit any data, or transmits very little data. It's able to gather data and location from the victim using unencrypted data sent over the control plane. These generally aren't able to extract as much data, or as accurately as active interception, but they're much harder to detect. Usually they aren't able to extract the device's IMSI for example. However, there was a recent paper describing a passive IMSI catcher that was both extremely hard to detect and great at tracking victims: https://www.usenix.org/system/files/sec22summer_kotuliak.pdf

If you'd like a more technical description about the techniques described I'd be happy to jump into that too.