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posted by martyb on Wednesday April 04 2018, @01:33PM   Printer-friendly
from the a-WOPR-of-a-story dept.

In a letter to Senator Ron Wyden, the Department of Homeland Security has acknowledged that unknown users are operating IMSI catchers in Washington, D.C.:

The Department of Homeland Security (DHS) is acknowledging for the first time that foreign actors or criminals are using eavesdropping devices to track cellphone activity in Washington, D.C., according to a letter obtained by The Hill.

DHS in a letter to Sen. Ron Wyden (D-Ore.) last Monday said they came across unauthorized cell-site simulators in the Washington, D.C., area last year. Such devices, also known as "stingrays," can track a user's location data through their mobile phones and can intercept cellphone calls and messages.

[...] DHS official Christopher Krebs, the top official leading the NPPD, added in a separate letter accompanying his response that such use "of IMSI catchers by malicious actors to track and monitor cellular users is unlawful and threatens the security of communications, resulting in safety, economic and privacy risks."

DHS said they have not determined the users behind such eavesdropping devices, nor the type of devices being used. The agency also did not elaborate on how many devices it unearthed, nor where authorities located them.

Also at Ars Technica and CNN.

Related: Police: Stingray Device Intercepts Mobile Phones
ACLU Reveals Greater Extent of FBI and Law Enforcement "Stingray" Use
US IRS Bought Stingray, Stingray II, and Hailstorm IMSI-Catchers
EFF Launches the Cell-Site Simulator Section of Street Level Surveillance
NYPD Making Heavy Use of Stingrays
New York Lawmakers Want Local Cops to Get Warrant Before Using Stingray
New Jersey State Police Spent $850,000 on Harris Corp. Stingray Devices


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  • (Score: 2) by Bobs on Wednesday April 04 2018, @03:29PM (5 children)

    by Bobs (1462) on Wednesday April 04 2018, @03:29PM (#662515)

    I literally do not know what I am talking about.

    But, as they are all fake cell towers, and people have access to handheld smart-phones, it seems like a software problem to me.

    Get 20+ people spread out with a smart phone and special software, all log into a site where you upload the cell connection data from the phones in real time, server filters out the known/registered towers and people converge on an area. Apparently they already have a general/regional map of problem IMSIs in DC area.

    Seems like you would able to quickly filter out the noise and reflections based upon the multiple inputs and quickly triangulate a bad source. Flag it and tag and and move on to the next.

    I am certain there is a lot of complexity I am missing - feel free to point out the flaws of this.

    Thanks.

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  • (Score: 3, Interesting) by Knowledge Troll on Wednesday April 04 2018, @03:44PM (4 children)

    by Knowledge Troll (5948) on Wednesday April 04 2018, @03:44PM (#662520) Homepage Journal

    I literally do not know what I am talking about.

    Not always a bad thing. Approaching this with out the limitations/bias I bring from doing previous DF actually helped me realize I'm outside my domain of expertise because cell phones have a very different signal with characteristics that enable what starts to look like pure voodoo.

    First of all the thought came to mind that the cell system can already locate cell phones using direction finding with cooperating cell towers and the accuracy is down in the 10s to 100s of meters as I recall. This is done with time difference of arrival analysis I believe and requires that the cell towers (specifically the DF receivers) are coherent which they are because all participants in the cell network are synchronized in time via GPS.

    If the cell towers can do this for cell phones they can most likely be modified/software updated to be able to do this for cell towers/stingrays and not just the cell phones themselves. This may assume that the device being located is cooperating or not actively trying to hinder the process.

    But more to your point about using all of the cell phones out there as receivers in a distributed DF network - not bad. Not bad at all. You got me thinking - all of those cell phones are also phase coherent with the other phones and the cell network as a whole because they synchronize to the towers which synchronize to GPS (the towers are STRAT 1 time sources). That is actually an amazingly powerful system!

    If you can get all of those receivers running at once, sending their received signals back to a central point along with the time information and the physical location of the phone, you can start to do time difference of arrival calculations with many more sources, assuming you through an absolute fuck ton of math at it.

    If you want to throw an even bigger absolute fuck ton at it, my estimate is about 20db more math, then you can start doing phased array DSP and form virtual directional antennas that you can rotate in space and have very sharp areas in them that you can exploit for direction finding. You could also do this as a DVR like system so you don't have to do all the analysis in real time - you could sit and study such signals and find other ones at your leisure (assuming you aren't trying to find a moving target).

    That might even let you find the exact phones sitting right next to the person if they were literally on all sides of them. It seems like having this on every phone in a city and the target being on the road would let this happen.

    I suppose this is within the realms of the NSA but it is getting outside my domain of expertise too. I'm not that sophisticated with radios.

    • (Score: 2) by Osamabobama on Wednesday April 04 2018, @06:07PM (1 child)

      by Osamabobama (5842) on Wednesday April 04 2018, @06:07PM (#662572)

      This could be a good (read compelling) use of the backdoors that NSA likely has in most cell phones.

      Outside of the NSA, I'm sure there would be a community of people interested in crowd-sourcing this effort, as long as the results were published. Something along the lines of Folding@Home, but for cell phones. I suppose all that math you referred to would require some backend server to do the heavy lifting.

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      • (Score: 2) by Knowledge Troll on Wednesday April 04 2018, @09:28PM

        by Knowledge Troll (5948) on Wednesday April 04 2018, @09:28PM (#662643) Homepage Journal

        Well one issue that is going to be a problem is I don't think the average cell phone is going to do this with out some kind of modification. I heavily suspect the interface available to the baseband module just won't allow for operating it/getting information out of it in a way where all the detail would be available. Though for a good chunk of them there is quite likely a new firmware that could be loaded into the baseband module if it uses SDR.

    • (Score: 2) by JoeMerchant on Wednesday April 04 2018, @07:27PM

      by JoeMerchant (3937) on Wednesday April 04 2018, @07:27PM (#662596)

      There's a company around Vero Beach that does triangulation based on TOF measurements - mostly for first responder radios, but the idea is that with 3 or more receiver towers, you can track the difference in time of arrival of a particular signal and get a rough idea where it came from. Like the urban gunshot locators, but with radio (only ~7 orders of magnitude faster, WGCW?)

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    • (Score: 0) by Anonymous Coward on Wednesday April 04 2018, @07:28PM

      by Anonymous Coward on Wednesday April 04 2018, @07:28PM (#662598)

      If reflections are such a huge problem, would it be simpler from an aerial perspective? I would imagine a few drones working together could narrow in on one fairly quickly.

      Though most low flying drones aren't very stealthy ...