Although I personally wouldn't usually say that anything that messes with someone's computer without their concent is "good" in any way shape or form, I've gotta say that I see little harm in this.

I mean, yeah, most tech-savvy people out there patched up their systems and were ready for this. But there's a lot of people that either didn't know about it or didn't know how to handle it or whatever. If Blaster got into their systems they'd either be stuck with computers that suck, or wind up paying some tech money to come and perform the obcenely simple fix. If this Nachi will take care of that problem, then it saves the tech time, the customer money, and helps put an end to Blaster and all the variants that have, and will inevitably, pop up.

I can't say I approve, but I would like to shake the hand of whoever made it for their sheer ingenuity in turning the virus against itself.