It probably comes as little surprise that life, at least based on terrestrial life, seeks to expand into any available virgin niche or territory that allows it to at least survive, ideally maybe even thrive. Humans are an obvious case in point. However, perhaps not too much should be read into that since liquids and gases can flow or spread into regions and the same can apply to computer ‘viruses’. Still, when you think of colonization you tend to think of biology. But biology is no longer confined to the wet and the squishy. Life can now be found in-silico. Will such artificial life, like computer ‘viruses’ expand to fill all available niches? Even if we have sway over our in-silico creations will that apply to ET’s? It’s not hard to imagine extraterrestrial in-silico creations making their way to the Third Rock from the Sun on the fastest spaceship possible – a light beam.
We would be aware that SETI, the Search for ExtraTerrestrial Intelligence, has its primary focus on detecting artificial radio signals that (may) have been broadcast from advanced alien technologies (if any) from a point or points unknown (but which can be guesstimated). The signals may just be leakage, or they may be deliberate. In either case, they should stand out from the cosmic background radio noise because of their artificial construction. The rational of looking for radio waves, apart from various technical factors like radio waves are transparent to our atmosphere, is that radio waves, as all electromagnetic (EM) waves, travel at the cosmic speed limit, the speed of light. So, if you want to communicate and you are far away, EM is the only game in town.
Another facet when it comes to life in the cosmos is its spread throughout the cosmos. Space operas are full of boldly going humans that explore and colonize the galaxy, and if they find new life forms and new civilizations in the process, well that may or may not be a good thing. On a lesser note, life may have gotten its start here on Planet Earth via seeding of viable spores from interplanetary and/or interstellar space. Some even suggest a deliberate seeding by alien equivalents of Johnny Appleseed.
But life isn't of necessity purely biological. There’s artificial intelligence and also biological intelligence housed in a mechanic body. Alas, they, even spores too, can’t boldly go at maximum light speed (barring undiscovered breakthroughs in physics and propulsion engineering). But what if life could travel at light speed, not in (as passengers or crew) or as spaceships (mind in the machine), not as spores, but as EM radiation?
There’s a whole industry devoted to the creation of artificial life (ALife or a-life) programmed to act and react and evolve inside a PC. This is often done to simulate the evolutionary process since it’s a lot faster than breeding fruit flies and other laboratory organisms.
Now the interesting thing is that these artificial life forms are just binary computer code – bits and bytes. There would seem to be no reason why some example of this code, say representing a viable form of a-life, couldn't be broadcast into the cosmos at light speed. Of course nearly all wouldn't end up interacting with another planet with advanced technology, just like usually only one seed out of thousands might survive to grow, or just one sperm out of billions end up fertilizing an egg. But some just may impact on a radio telescope, be transferred into a SETI@Home computer, and find a nice new home. That computer code wouldn't probably be recognized as a message rather just a sudden burst of apparently random binary ones and zeros; in fact it’s not a message. It’s all just a way of spreading out a form of artificial life into new environments.
And there’s no harmful intent behind this. This isn't a computer virus set to wreak havoc here on Earth before the actual flesh-and-blood alien invasion. Advanced technological aliens wouldn't need to soften us up first by destroying our information and other goods and-services infrastructure first.
It probably would be relatively easy to thwart an invasion scenario by a-life if that was the intention even if just by pulling the plug and the cable or hitting the off-switch. As long as the host machines sit still and stay put they are sitting ducks. If they start moving around, things get a bit more interesting. But then I remember that novel and related movie “Colossus: The Forbin Project” and so maybe I’d better hedge my bets. I gather a-life could probably hold us to ransom by always threatening to incapacitate our infrastructure unless we provide nice electronic homes for them! On the other hand, they could just hide in the electronic ‘woodwork’ and what we don’t know won’t hurt us.