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diff --git a/articles/2023-07-12-mic-rf-interference.md b/articles/2023-07-12-mic-rf-interference.md deleted file mode 100644 index e8b2696..0000000 --- a/articles/2023-07-12-mic-rf-interference.md +++ /dev/null @@ -1,42 +0,0 @@ -# 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). - -**Update:** I have done some research and recognized that this is actually a -very common problem and that it also occcurs on otther machines. People were -even able to decode emission vom VGA and DVI cables to recover the pictures that -is sent. Crazy! - - |