I got the same notification last Tuesday. I was switching between websites - USA Today and this one, when the Norton window popped up in the lower right hand corner of my screen.
To the best of my recollection, it said:
Norton anti-virus/worm intrusion protection has detected and blocked NetBus - a Trojan Horse worm from entering your computer.
Time: 9:36am
Date: Aug 16, 2005
Path: N/A
I recall a bunch of PCs all across the states got hit with an intrusion on their Windows 2000 OSs, but I'm not sure if it was part of this one.
I checked "quarrantine" and there's nothing in there about any worm, so it must have gone "poof", I suppose.
I just Googled "NetBus Trojan Horse", and got this:
NetBus Pro 2.1 is a remote administration and monitoring tool from UltraAccess Networks, Inc.
Norton suggests you disable ALL remote access to your PC. This worm has been around since 2001!