I just got a reply from the spammer's ISP

Alan Erskine wrote:
Despite the headers saying it was coming from "usenetnow.com", it was
actually coming from an account at "usnetnow.net" - I went to that site and
left a formal complaint; this is the reply in full:

Hi-
Thanks. We took care of it.
===========
Scott
UseNetNow.Net Support

That's all I got, but hopefully, the spammer is gone!

Yea... guessing by the baker's dozen posted since your post, I'd say you
alerted them that someone actually reads these groups and as such have
redoubled their efforts...

I've just gotten use to using "K" hotkey in Thunderbird to ignore those
threads...