Indeed, I mean these days the checkers, atleast from the windows based ones I've experienced, tend to check "the possibility that something is a virus" by comparing a trait with what a file looks like, often from signitures of tell-tale signs. This ofc has good and bad points. Bad points can include the scanners automatically removing files that are simply not a problem, but by their nature hold something close to a signiture.
Many moons ago, it was the case where viruses in their entirity where part of the db that scanners/checkers used. In these cases also there would be a %age check as to whether variants were the infections. Would also be the case that in order to apply fixes for various viruses that u could actually apply the viruses themselves. This could be helpful for testing, but ofc also leathal in the wrong hands. With the internet world, those hands are everywhere.
What would bother me perhaps is that with the fashion of checking for viruses being more and more concentrated on immediate threats from new variants, that older ones are perhaps overlooked in some way. A 10 year old usb drive gets plugged in by a firm and all hell breaks loose.
It'd be interesting to check on all platforms certainly.
