The Bulbs Have Ears: Bugging Incandescent & LED Lights (and weird science)

A little while ago ‘the grugq’ posted an intriguing excerpt from a book, suggesting incandescent light bulbs are easy to turn into listening devices.[1] (Unfortunately, it’s not clear what book this is from — anyone know?)

The general concept seems to revolve around the filament. It’s an easily-rattled hot glowing wire, which is another way of saying “dipole antenna spatially modulated by room audio.”

If you “light up” said antenna with an external radio signal, it may be possible to recover room audio based on the doppler shift. (Perhaps an application for a lock-in amplifier? I’m a little rusty in this area, forgive me if I’m off)

The citation suggests flourescent ligths are the solution, but — screw that. This is one place where I’m willing to trade off security for the warm, continuous-spectrum glow of a black-body radiator… instead of the abomination that is flourescent light.

It also turns out that switching to LEDs won’t necessarily help either. Details are very scarce so this could be disinformation or just regular fear-mongering, but it seems there are some LEDs which can be modified to exfiltrate room audio. Fortunately, this seems to require physical access to the space, so it’s less of an issue than the incandescents. (LED light still sucks, though.)

Weird science bonus: the second citation [2] mentions an “inductive device” that “literally goes through anything and it is very scary.” While it’s certainly possible that someone built a bug with a tiny tuned magnetic loop to exfiltrate audio via VLF/ELF… given the context I’m wondering if this isn’t Tesla technology poking out of the shadows. (A lot of the stuff Tesla worked with was well-nigh impossible to shield.)



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