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diff --git a/articles/2023-07-12-mic-rf-interference.md b/articles/2023-07-12-mic-rf-interference.md new file mode 100644 index 0000000..73e8afa --- /dev/null +++ b/articles/2023-07-12-mic-rf-interference.md @@ -0,0 +1,38 @@ +# Spying on microphones through electrical interference (or something along those lines) + +Today I was using my `rtl2832u`-based software defined radio to listen to air +traffic control and such. At some point when I was scanning around in 6m +Ham-Band I noticed two pretty strong signals. I was suprised to even find +anything with an antenna only 50cm of length. However when I +frequency-demodulated any of the two signals I was able to hear myself speak. At +that point I got _slightly_ creeped out and started investigating. + +I was able to confirm that the audio was what is being recorded by my laptop's +built-in microphone. My first hypothesis was that this was not actually +broadcast but just interference because the SDR is in the same electrical +circuit as the rest of my laptop. + +Later I tried to check if this is a problem in laptops in general by my friend +testing it on their laptop. This did yield an audio signal, however the one of +**my** laptop! (They were positioned about 1m apart.) + +When I arrived at home I tried spying on my laptop's mic but wasn't able to +reproduce this behaviour if it was not in the same circuit. + +I would really like to know why this is happening. I still can't explain why the +signal is frequency modulated and why it is carried by such a high frequency +(around 50MHz). In case you want to reproduce, here are some details about the +setup: + +- Laptop: Acer Nitro AN515-43 +- SDR: Nooelec NESDR SMArt v5 +- Frequency: 52.125 MHz + +In the scenario where this can actually be received from nearby, this is a +somewhat critical security problem since even keystrokes might be recovered from +the audio. + +Also if you have any expertise or clues please [contact me](/contact). + + + |