I knew that it was possible to spy on CRT displays due to the signals they radiate, but apparently that is a problem with HDMI too.

Here a very interesting write up on how to extract frames from leaked RF from HDMI cables and using said RF to transmit a webcam stream even: https://www.windytan.com/2023/02/using-hdmi-radio-interference-for-high.html

Here a example of someone using HDMI RF to transmit LoRa signals: https://www.youtube.com/watch?v=HDbdAZd6cLw

This makes for a interesting attack vector for locating a user, if said user clicks on a video (or even a gif) that crafts LoRa frames to radiate from his HDMI and there is for example a Meshtastic receiver near by that relays those frames into a wider network.

There are ways to migrate this issue, for example using the encrypted version of HDMI usually used to enforce content copyright protection, or using a fiber optic HDMI cable (by now they are almost as cheap as the copper ones and are not restricted to a max lenght of 5m).

  • NaibofTabr@infosec.pubEnglish
    20·
    17 hours ago

    Would ferrite beads be a cheap and simple solution for this? You can buy them as clip-ons for cables that don’t have them built in.

    This makes for a interesting attack vector for locating a user, if said user clicks on a video (or even a gif) that crafts LoRa frames to radiate from his HDMI and there is for example a Meshtastic receiver near by that relays those frames into a wider network.

    Also, I’m not sure I see the point of this… if you already know where the HDMI cable is with enough accuracy to collect low-power radio emissions, then you already know the user’s location - they’re probably pretty close to the monitor that the HDMI cable is plugged into.

    • HAL_9_TRILLION@lemmy.dbzer0.com
      4·
      11 hours ago

      Also, I’m not sure I see the point of this… if you already know where the HDMI cable is with enough accuracy to collect low-power radio emissions, then you already know the user’s location

      Well the other half of it is that whatever media is being run through the cable is compromised so that it emits RF that is recognizable to a LoRa device. Such a device would think it was coming from another Meshtastic device and would therefore pick it up and broadcast it, which could serve to locate someone in a wide area.

      So it’s interesting, but it seems pretty niche. You can deliver compromised media to someone you can’t locate AND they are a Meshtastic hobbyist… yeah not likely.