Theoretically possible, but nowhere near as easy as you might think. I have some photos somewhere of what was a top secret US military modem, designed to be a secure link to satellites. This was, at the time, a development project, not a published photo. This "modem" was a size of a couple of large filing cabinets, and I could probably have stood up inside an empty cabinet, or certainly, not far off doing so. It had world-class (and I do mean that) encryption, and both the uplink and the satellite were frequency "agile" ... in other words, they frequency-hopped, not only to prevent interception, but to prevent jamming. Even if a hacker could find the frequency it operated on, seconds later, it wouldn't be there. This modem had, if memory serves, something like 50 different processor boards in it.
And
that technology was a Reagan-era Star Wars device, from the thick end of 30 years ago. If it still exists, it's probably in a museum somewhere. And I don't even want to think about what it cost. So if that's what they were using when most of us probably hadn't seen a PC and certainly didn't own one, it invites speculation as to what they use now, doesn't it?
