blog/data/2017-09-29-gsm-imsi-catcher.txt

   1 Title: Visualizing GSM radio chatter using gr-gsm and Hopglass
   2 Tags: english, debian, personvern, surveillance
   3 Date: 2017-09-29 10:30
   4
   5 <p>Every mobile phone announce its existence over radio to the nearby
   6 mobile cell towers.  And this radio chatter is available for anyone
   7 with a radio receiver capable of receiving them.  Details about the
   8 mobile phones with very good accuracy is of course collected by the
   9 phone companies, but this is not the topic of this blog post.  The
  10 mobile phone radio chatter make it possible to figure out when a cell
  11 phone is nearby, as it include the SIM card ID (IMSI).  By paying
  12 attention over time, one can see when a phone arrive and when it leave
  13 an area.  I believe it would be nice to make this information more
  14 available to the general public, to make more people aware of how
  15 their phones are announcing their whereabouts to anyone that care to
  16 listen.</p>
  17
  18 <p>I am very happy to report that we managed to get something
  19 visualizing this information up and running for
  20 <a href="http://norwaymakers.org/osf17">Oslo Skaperfestival 2017</a>
  21 (Oslo Makers Festival) taking place today and tomorrow at Deichmanske
  22 library.  The solution is based on the
  23 <a href="http://people.skolelinux.org/pere/blog/Easier_recipe_to_observe_the_cell_phones_around_you.html">simple
  24 recipe for listening to GSM chatter</a> I posted a few days ago, and
  25 will show up at the stand of <a href="http://sonen.ifi.uio.no/">Åpen
  26 Sone from the Computer Science department of the University of
  27 Oslo</a>.  The presentation will show the nearby mobile phones (aka
  28 IMSIs) as dots in a web browser graph, with lines to the dot
  29 representing mobile base station it is talking to. It was working in
  30 the lab yesterday, and was moved into place this morning.</p>
  31
  32 <p>We set up a fairly powerful desktop machine using Debian
  33 Buster/Testing with several (five, I believe) RTL2838 DVB-T receivers
  34 connected and visualize the visible cell phone towers using an
  35 <a href="https://github.com/marlow925/hopglass">English version of
  36 Hopglass</a>.  A fairly powerfull machine is needed as the
  37 grgsm_livemon_headless processes from
  38 <a href="https://tracker.debian.org/pkg/gr-gsm">gr-gsm</a> converting
  39 the radio signal to data packages is quite CPU intensive.</p>
  40
  41 <p>The frequencies to listen to, are identified using a slightly
  42 patched scan-and-livemon (to set the --args values for each receiver),
  43 and the Hopglass data is generated using the
  44 <a href="https://github.com/petterreinholdtsen/IMSI-catcher/tree/meshviewer-output">patches
  45 in my meshviewer-output branch</a>.  For some reason we could not get
  46 more than four SDRs working.  There is also a geographical map trying
  47 to show the location of the base stations, but I believe their
  48 coordinates are hardcoded to some random location in Germany, I
  49 believe.  The code should be replaced with code to look up location in
  50 a text file, a sqlite database or one of the online databases
  51 mentioned in
  52 <a href="https://github.com/Oros42/IMSI-catcher/issues/14">the github
  53 issue for the topic</a>.
  54
  55 <p>If this sound interesting, visit the stand at the festival!</p>