Thursday, December 20, 2012

Radio Frequency Exploitation using GNU Radio + USRP2: Part 2

Hi folks.
Welcome to part two of this topic.  Picking up from where we left from, we have our USRP + Gnuradio glued together neatly and so where do we go from here?

Well, like I had stated before, the potential for this sort of 'hackery' is incredible and today ill demonstrate just that.

There is no plug and play radio interceptors though some folks have been kind enough to make work easier. Gnuradio is ideally an SDK in itself with loads of libraries which assist one to develop their own fancy tools to play with the radio interface. Also of interest is the GNU Radio Companion which provides an environment to develop your own Flow Graphs and also Flow graph source code. It's pretty neat and I would recommend this site http://gnuradio.org/redmine/projects/gnuradio/wiki/Tutorials for anyone who is starting off with SDR( Software Defined Radio).

GRC comes with examples of basic receivers and transmitters. These include a basic wide band FM receiver (wfm), tv receiver, narrow band FM receivers, etc. Again there are tonnes of material out there on how GNU Radio works coupled with the various sinks included. However, this guy  has some neat implementations which with a bit of tweaking makes signal process programming quite easy.
I borrowed some of his implementations and tweaked them to suite my environment especially for the WFM, NOAA and APT receivers. Please note ill just demo on reception since I dont possess a license to transmit. CCK will be hot on my heels so let's stick to what is publicly available.

This video will show you how with the right antennae and of course with allocated frequency bands well advertised on the CCK website I thought to myself why not? Besides, it simply goes to show that law enforcement communication isn't encrypted and it begs the question why it isn't. Besides, there exist HF encryption technologies to prevent such kind of interceptions like the Project 25(P25 or APCO-25) which is a standard that defines digital radio communication.

In a nutshell, the receiver used in the clip is an FM receiver coupled with the USRP communicating via UHD. Notice the FFT (Full Fourier Transform) and the peak hold indicating the top frequency range for the communication.
 These by the way are different police allotments; Traffic and General Police.

Have fun... see you in Part 3 where we shall look at Air Traffic interception.






-ty