Just because you can't fathom a world where this could be true (too scary, etc.) or because there is some lack of logic or feasibility?
Lack of logic, feasibility and credibility.
Like the virus it claims, the article also make sure that this can't be verified and that even after reading it, you can't do anything about it.
So how is this useful?
Computer security for large enterprises is what I do for a living. If this was your trade, you'd recognize the B.S. just as well.
Edit: Don't get me wrong... there are some very complex virus, who avoids detection with sophisticated algorithms that allows the code to rewrite itself constantly thus not leaving an easily recognizable signature.
But, the article stipulates they know who did this (6 years ago). There would have been ample time to have them reproduce the code, and then devise an inoculation. You think not?
The creators also are young adults with no agenda apparently; they would surely had cooperated in providing all the information necessary to deal with this situation.
It's also more then likely that the OS they wrote this for (assuming windows 2000) is only marginally used today, and that most computers since then possibly infected are no longer in operation, upgraded or patched.
Also, classified information do get leaked... but rarely does the leaker exposes himself in a way that he can be easily identified. This chain from; - conversation at lunch - to - blogged on a highly politicized newsletter - just as no credibility to my eyes.