- <title>Simpler recipe on how to make a simple $7 IMSI Catcher using Debian</title>
- <link>http://people.skolelinux.org/pere/blog/Simpler_recipe_on_how_to_make_a_simple__7_IMSI_Catcher_using_Debian.html</link>
- <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Simpler_recipe_on_how_to_make_a_simple__7_IMSI_Catcher_using_Debian.html</guid>
- <pubDate>Wed, 9 Aug 2017 23:59:00 +0200</pubDate>
- <description><p>On friday, I came across an interesting article in the Norwegian
-web based ICT news magazine digi.no on
-<a href="https://www.digi.no/artikler/sikkerhetsforsker-lagde-enkel-imsi-catcher-for-60-kroner-na-kan-mobiler-kartlegges-av-alle/398588">how
-to collect the IMSI numbers of nearby cell phones</a> using the cheap
-DVB-T software defined radios. The article refered to instructions
-and <a href="https://www.youtube.com/watch?v=UjwgNd_as30">a recipe by
-Keld Norman on Youtube on how to make a simple $7 IMSI Catcher</a>, and I decided to test them out.</p>
-
-<p>The instructions said to use Ubuntu, install pip using apt (to
-bypass apt), use pip to install pybombs (to bypass both apt and pip),
-and the ask pybombs to fetch and build everything you need from
-scratch. I wanted to see if I could do the same on the most recent
-Debian packages, but this did not work because pybombs tried to build
-stuff that no longer build with the most recent openssl library or
-some other version skew problem. While trying to get this recipe
-working, I learned that the apt->pip->pybombs route was a long detour,
-and the only piece of software dependency missing in Debian was the
-gr-gsm package. I also found out that the lead upstream developer of
-gr-gsm (the name stand for GNU Radio GSM) project already had a set of
-Debian packages provided in an Ubuntu PPA repository. All I needed to
-do was to dget the Debian source package and built it.</p>
-
-<p>The IMSI collector is a python script listening for packages on the
-loopback network device and printing to the terminal some specific GSM
-packages with IMSI numbers in them. The code is fairly short and easy
-to understand. The reason this work is because gr-gsm include a tool
-to read GSM data from a software defined radio like a DVB-T USB stick
-and other software defined radios, decode them and inject them into a
-network device on your Linux machine (using the loopback device by
-default). This proved to work just fine, and I've been testing the
-collector for a few days now.</p>
-
-<p>The updated and simpler recipe is thus to</p>
-
-<ol>
-
-<li>start with a Debian machine running Stretch or newer,</li>
-
-<li>build and install the gr-gsm package available from
-<a href="http://ppa.launchpad.net/ptrkrysik/gr-gsm/ubuntu/pool/main/g/gr-gsm/">http://ppa.launchpad.net/ptrkrysik/gr-gsm/ubuntu/pool/main/g/gr-gsm/</a>,</li>
-
-<li>clone the git repostory from <a href="https://github.com/Oros42/IMSI-catcher">https://github.com/Oros42/IMSI-catcher</a>,</li>
-
-<li>run grgsm_livemon and adjust the frequency until the terminal
-where it was started is filled with a stream of text (meaning you
-found a GSM station).</li>
-
-<li>go into the IMSI-catcher directory and run 'sudo python simple_IMSI-catcher.py' to extract the IMSI numbers.</li>
-
-</ol>
-
-<p>To make it even easier in the future to get this sniffer up and
-running, I decided to package
-<a href="https://github.com/ptrkrysik/gr-gsm/">the gr-gsm project</a>
-for Debian (<a href="https://bugs.debian.org/871055">WNPP
-#871055</a>), and the package was uploaded into the NEW queue today.
-Luckily the gnuradio maintainer has promised to help me, as I do not
-know much about gnuradio stuff yet.</p>
-
-<p>I doubt this "IMSI cacher" is anywhere near as powerfull as
-commercial tools like
-<a href="https://www.thespyphone.com/portable-imsi-imei-catcher/">The
-Spy Phone Portable IMSI / IMEI Catcher</a> or the
-<a href="https://en.wikipedia.org/wiki/Stingray_phone_tracker">Harris
-Stingray</a>, but I hope the existance of cheap alternatives can make
-more people realise how their whereabouts when carrying a cell phone
-is easily tracked. Seeing the data flow on the screen, realizing that
-I live close to a police station and knowing that the police is also
-wearing cell phones, I wonder how hard it would be for criminals to
-track the position of the police officers to discover when there are
-police near by, or for foreign military forces to track the location
-of the Norwegian military forces, or for anyone to track the location
-of government officials...</p>
-
-<p>It is worth noting that the data reported by the IMSI-catcher
-script mentioned above is only a fraction of the data broadcasted on
-the GSM network. It will only collect one frequency at the time,
-while a typical phone will be using several frequencies, and not all
-phones will be using the frequencies tracked by the grgsm_livemod
-program. Also, there is a lot of radio chatter being ignored by the
-simple_IMSI-catcher script, which would be collected by extending the
-parser code. I wonder if gr-gsm can be set up to listen to more than
-one frequency?</p>
+ <title>Measuring the speaker frequency response using the AUDMES free software GUI - nice free software</title>
+ <link>http://people.skolelinux.org/pere/blog/Measuring_the_speaker_frequency_response_using_the_AUDMES_free_software_GUI___nice_free_software.html</link>
+ <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Measuring_the_speaker_frequency_response_using_the_AUDMES_free_software_GUI___nice_free_software.html</guid>
+ <pubDate>Mon, 22 Oct 2018 08:40:00 +0200</pubDate>
+ <description><p><img src="http://people.skolelinux.org/pere/blog/images/2018-10-22-audmes-measure-speakers.png" align="right" width="40%"/></p>
+
+<p>My current home stereo is a patchwork of various pieces I got on
+flee markeds over the years. It is amazing what kind of equipment
+show up there. I've been wondering for a while if it was possible to
+measure how well this equipment is working together, and decided to
+see how far I could get using free software. After trawling the web I
+came across an article from DIY Audio and Video on
+<a href="https://www.diyaudioandvideo.com/Tutorial/SpeakerResponseTesting/">Speaker
+Testing and Analysis</a> describing how to test speakers, and it listing
+several software options, among them
+<a href="https://sourceforge.net/projects/audmes/">AUDio MEasurement
+System (AUDMES)</a>. It is the only free software system I could find
+focusing on measuring speakers and audio frequency response. In the
+process I also found an interesting article from NOVO on
+<a href="http://novo.press/understanding-speaker-specifications-and-frequency-response/">Understanding
+Speaker Specifications and Frequency Response</a> and an article from
+ecoustics on
+<a href="https://www.ecoustics.com/articles/understanding-speaker-frequency-response/">Understanding
+Speaker Frequency Response</a>, with a lot of information on what to
+look for and how to interpret the graphs. Armed with this knowledge,
+I set out to measure the state of my speakers.</p>
+
+<p>The first hurdle was that AUDMES hadn't seen a commit for 10 years
+and did not build with current compilers and libraries. I got in
+touch with its author, who no longer was spending time on the program
+but gave me write access to the subversion repository on Sourceforge.
+The end result is that now the code build on Linux and is capable of
+saving and loading the collected frequency response data in CSV
+format. The application is quite nice and flexible, and I was able to
+select the input and output audio interfaces independently. This made
+it possible to use a USB mixer as the input source, while sending
+output via my laptop headphone connection. I lacked the hardware and
+cabling to figure out a different way to get independent cabling to
+speakers and microphone.</p>
+
+<p>Using this setup I could see how a large range of high frequencies
+apparently were not making it out of my speakers. The picture show
+the frequency response measurement of one of the speakers. Note the
+frequency lines seem to be slightly misaligned, compared to the CSV
+output from the program. I can not hear several of these are high
+frequencies, according to measurement from
+<a href="http://freehearingtestsoftware.com">Free Hearing Test
+Software</a>, an freeware system to measure your hearing (still
+looking for a free software alternative), so I do not know if they are
+coming out out the speakers. I thus do not quite know how to figure
+out if the missing frequencies is a problem with the microphone, the
+amplifier or the speakers, but I managed to rule out the audio card in my
+PC by measuring my Bose noise canceling headset using its own
+microphone. This setup was able to see the high frequency tones, so
+the problem with my stereo had to be in the amplifier or speakers.</p>
+
+<p>Anyway, to try to role out one factor I ended up picking up a new
+set of speakers at a flee marked, and these work a lot better than the
+old speakers, so I guess the microphone and amplifier is OK. If you
+need to measure your own speakers, check out AUDMES. If more people
+get involved, perhaps the project could become good enough to
+<a href="https://bugs.debian.org/910876">include in Debian</a>? And if
+you know of some other free software to measure speakers and amplifier
+performance, please let me know. I am aware of the freeware option
+<a href="https://www.roomeqwizard.com/">REW</a>, but I want something
+that can be developed also when the vendor looses interest.</p>
+
+<p>As usual, if you use Bitcoin and want to show your support of my
+activities, please send Bitcoin donations to my address
+<b><a href="bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b">15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b</a></b>.</p>