I hope this is the right forum to ask this question. If not, please tell me where to go.
From my understanding most cables have an electromagnetic field around them when data passes through them and I think I remember having unexplainable issues with one of my TVs about 12 years ago where, when watching a VHS, I could still see a pale image of what was currently on TV in the background. I suspect that this had something to do with the bad insulation of the cables, but it also seems super unlikely that the image could be transmited to flalessly, so I don't know...
How conceivable would it be that, with the tech now available, we could build a device that could receive and process the data that is sent through a cable, without having physical contact with it?
I'm mostly thinking about USB and ethernet cables, but also about cables that have a lot of wires, like HDMI. And what about fiberglas cables?
Could it be possible that the NSA is spying on our ethernet cables without even thouching them?
And could you build a hardware keylogger that doesn't need to touch the keyboard's wires? (I'm obviously not talking about wireless keyboards.)
What would be a conceivable range for something like this to work in a realistic home with TVs, routers and smartphones sending their waves all day long?
How problematic is it that an HDMI cable has 19 wires? Would that interfere and make it inconceivable that someone could reproduce what is sent through the cable?
And what about injecting fake data into a cable? How conceivable is that?