Take a look at the page referred to by the URL:
It explains why there has been so much lately. The scoundrel responsible has been particularly clever in using it to harvest names and addresses from the Usenet newsgroups, both to target as recipients of the SPAM and to generate phony return addresses, and it appears to generate enough variability in both the subject header and the name of the attachment containing the worm that, at least my ISP's, anti-spam system doesn't catch but a tiny fraction of it.
The good news it that Norton's antivirus software recognizes it and protects from infection. I have received thousands of these things and still my system remains uncontaminated! Now, if only we could track down the worthless bastard(s) responsible for this, so we can obtain a little justice!
Cheers,
Ted