Actually in ID4 there was an explanation. Basically all of humanity's computer tech came from reverse engineering alien tech. So our computers worked with theirs because they were based on theirs. Maybe this isn't this best logic, but they did at least have an in universe explanation.
The ultimate security by obscurity. Do you have a 30m antenna? Can you point it exactly at the space ship with almost no error? Do you know what it's code and protocols are? OK, please reprogram Voyager
I mean, sure, technically. They'd have to know English, know the programming language that was used for the probe, know the transmission frequency that the probe accepts, know the boundaries and limitations of the probe so that they don't actually force any errors, and presumably would need to crack the encryption preventing anyone else from reprogramming Voyager 1. They'd also either need to be able to generate incredibly strong radio waves through space in order to transmit their code, or they'd need to be close enough to us that we'd be able to detect their presence.
While that's all technically possible, the odds of it happening are pretty low.
Crack encryption from the mid 70's? If there even is any on the Voyager command signal, I couldn't find a reference to any. But if there is, I'd think modern computers are up to the task.
They’d also either need to be able to generate incredibly strong radio waves through space
My guess is that THIS is the actual security feature.
Not to mention... who would even want to? There's nothing to gain except slight infamy, if you could even prove you were behind it.
Yes, one entity being able to reprogram one piece of tech definitely means another entity is able to reprogram every other piece of tech that is slightly related.
I mean... Can you reprogram Voyager 1? We have a bunch of random polyhedrons from the ancient world and we don't even know what the hell they are. Our stuff could be so ancient compared to an alien that they are just as baffled by it as we are of those polyhedrons.
They might not even be able to understand the simple pictorial instructions for playing the audio on the golden record Voyager carries.
There's a novel titled Glasshouse, by Charles Stross, where members of a far future civilization sign up to live in a simulated mid-20th century town. At one point the protagonist disassembles a flashlight and discovers that it's just a flashlight-shaped case containing a small wormhole whose other end is in close orbit around a star. No one knew how to make an LED or incandescent bulb, or understood enough about early electronic components to hook one up to a switch and a battery. It was easier to make a wormhole generator and stick it in a metal tube.
Any alien species that is aware of our satellites is so technically superior to us they wouldn't bother. The James Webb Telecope is our best, but we still aren't certain we've named all the planets in our own solar system.
Probably not all of them. The Voyager probes were launched in the 70s and they don't exactly need much encryption because they can only be programmed by someone with a massive transmitter.
All I can think of is alien adolescents reprogramming them to mess with humans. Fake invasion messages, alien memes. Like cowtipoing, but screwing with humans instead