Comment Remote exploit? (Score 1) 27
"The physical aspect really only means that you could not exploit this over the internet from another country, you would need to be some physical distance from the train [so] that your signal is still received."
If it is a passive signal, it seems like the only thing preventing that is a lack of transmit power, at least to within the limits of the curvature of the earth (or, depending on frequency, maybe not even beyond that limit). And it's hard to overestimate the potential for financial loss if someone remotely cracked into a SpaceX satellite and manipulated its SDR to send such a signal from space.
Even if the attack requires two-way communication, the attacker still wouldn't need to be close to the train; the signal generator would. Nothing prevents someone from maliciously dangling a battery-powered or solar-powered, cellular-capable pod off the edge of a highway bridge that crosses a railroad track and being half a continent away when actually triggering it.
On the flip side, the fact that this hasn't been exploited yet is a pretty strong indication that nobody is trying to attack us, making it likely a pretty low risk.