A computer virus that targets computer virii,is it possible?

I've spent alot of time getting virii on my computer and testing anti-virus programs.because of the various codes used in virii alot of AV software won't pick them all up.My question is could I write a virus that targets a virus?and what assembly language would be best?

A computer virus that targets computer virii,is it possible?malware

You're basically looking at taking an existing anti-virus engine and packaging it in virus form (ie. making it spread and distribute itself, and presumably, automatically update itself and report virus statistics, adapt to new viruses (impossible) etc).

There's nothing magic about viruses. Making an anti-virus virus won't magically make it better at detecting or removing other viruses (and other malware). It will still have exactly the same limitations as any other AV. Except it will be worse, because if everyone is infected by your AV virus, virus writers will be able to infect more PCs by targeting its security flaws; easily bypassing your AV virus, or even worse, hijacking their own malicious code into your existing propagation method.

And, it would still be illegal. The laws for unauthorized PC access do not distinguish between "good" or "bad" unauthorized access, merely the fact that you don't have permission. I'm sure in your mind you think you're doing the right thing; but if you force your wares down their throat, it's not. After all, that's how most malware starts - people trying to prove a point, disclose a software's flaws to everyone, and before you know it that friendly "hey, your PC is insecure!" prank turns into "oops, I deleted all your files".