Admittedly, the concept of a virus going around and fixing vulnerabilities is interesting, and has a lot to recommend it.

It also has many dangers--those too have been mentioned.

I think, though, one of the reasons why it should *not* happen is reasonably self-evident: Darwin.

Evolutionary theory is not confined to just animals and plants and such. The same prinicples can be used on any reasonably complex system. The internet as a system [ with the various servers and clients thereon as the organisms ] works in a sort of evolutionary fashion. Those servers and clients that survive are the most robust ones, the ones most suited for the environment in which they are placed. The ones that die are the ones that are not fit to survive.

Indeed, I'd almost postulate that regular viruses--the kind that harm, not the kind that heal--are an important, even vital part of the mix. They are the means by which selection can happen.

A virus that wanders around patching--making more 'fit'--various systems would change the nature of the system. Those people who put organisms into the system [ computers on the internet ] would not be as concerned with making sure they're capable of surviving "because the virus will take care of it." This means that those who distribute the software would have even less impetus than the already vague 'loss of sales' that they have to make a truly robust, fit, and decently survivable piece of machinery and software than they already do.

Though an unintended consequence could be a sort of underground open-source community of people writing these things. That could be interesting to watch....sort of a digital "Robin Hood and his Merry Men" idea.

Granted, my analogy has holes in it [ where do braindead IT managers who insist on insecure OS's come in? ], but I think y'all can see my point.