Monday, September 7, 2015

Jamming WiFi Channels with HackRF

We can easily capture signals going in a particular frequency using HackRF and also we can retransmit those data back to the air from the file. Here's how we use it to jam some wifi channels. To try this, first I checked what is the specific frequency channel, which is used by my laptop and the WiFi hotspot to communicated. We can find it out by using the following command.

iwlist wlan0 channel

It should list down all the available WiFi channels and at the end, the channel currently we are using. In my case, it was  channel 11 which operated in 2.462 GHz. Now it's time to try jamming. First we should record some data to a file. We can do it with the following command. The parameter -f specify the frequency we need to tune in to in Hz. Similarly the parameter -s specify the sampling rate which I have set to 20 MHz. Finally the parameter -l specify the LNA gain. Reading man files will provide more information about those stuff.

hackrf_transfer -r test.bin -f 2462000000 -s 20000000 -l 40

This command will run for a while and save data to the file test.bin and stop at some point. Still, the reason to stop in that way is mysterious to me. Anyway, now we have some captured data. We can transmit it back. Before doing so, open a new terminal and ping to some public IP address such as 8.8.8.8 so that we can continuously see the ICMP packets going and coming with round trip information. While having the ping command running in that terminal, run the following command from our original terminal. That -x parameter sets the Tx VGA gain.

hackrf_transfer -t test.bin -f 2462000000 -s 20000000 -x 47

During the time period of above transmission going on, we can see that the ping packets are getting disturbed. Either they take a longer round trip delay or completely become unable to be delivered.

Here's a reference I used,


4 comments:

  1. Good Article!
    hi, I come from China,and i work on wireless router research, i bought a HackRF too, so i am thinking about how to take the HackRF as a Wifi tester...

    ReplyDelete
  2. Thanks :)
    Anyway, what do you mean by a wifi tester? You mean, using hackrf as a wifi spectrum analyzer or something like that?

    ReplyDelete
  3. This was exactly the information I needed. Thanks so much for your contribution.

    ReplyDelete
  4. Interesting, although it does rely on you manually tuning to the right frequency i.e. channel 11. Would it be possible to make the HackRF scan all the wifi channels, determine which one(s) are active, and then automatically jam those?

    ReplyDelete