This isn't a mutation, it's not evolution of bodies, but perhaps it is the creation of an ecosystem. This is the first (observed) occurance of something so cooperative between two such bodies of code.
Now, given that Klez happens to be good at running around the net, it seems to be the perfect vessel for lesser apt, but more specialized bodies of code to perpetuate. Older viruses aren't much in circulation, probably because an infected program would become noticed as a culprit and then be wiped or disinfected, once the infection was detected.
A worm, however, is special in that it spreads on its own. It doesn't reside on your harddrive so much as it is a phenomenon that occurs across the net. You can't isolate it to your harddrive, and you can't rid yourself of it simply by removing it because it will probably come to you again. You can protect yourself from it, however, but that's not important to my argument.
I have to wonder, though, which kind of virus would be able to best take advantage of the phenomenon. A destructive virus might destroy all of the participating hosts and wipe itself out. A moderately destructive one might manage to stay alive longer. The more I think about it, though, the more I believe that, provided the virus doesn't wreak havoc immediately, any degree of damage can be done and, aside from drawing more attention to itself, it is in little danger of causing its own extinction.
Just when I was considering getting back into writing redcode.
farq will not be coming back