I think they're just talking about the plain knowledge that the worm existed, and how to patch their computers to block it. If you go back a couple paragraphs, you'll see the writer's talking about the problems the government is having getting the private networks interconnected with the government's computers to get around to patching their systems, leaving them very vulnerable, and thus leaving the government vulnerable, since they rely on those private companies for many vital communications.
I don't recall there being anything particularly special about the NIMDA worm itself, other than its extreme annoyance factor. But then, I use a Mac and don't have to keep up with such things. *grin*
No, I don't think that's what they meant.
The existence and virulence of the worm were known very quickly; within just a few hours of Nimda's release, Atty. Gen. Ashcroft was on television to say that the government knew of no connection with 9/11.
The various antivirus companies and security experts analyzed the workings of Nimda extensively and publicized their findings. Microsoft put out a patch for IIS.
None of these things would have been facts that the government did not learn "until the stricken companies began firing their security executives."
Maybe this is just reporter's nonsense, I don't know. Were any security executives fired as a result of Nimda? If so, why?