I’m still quite a heavy user of Usenet, despite the influx of spammers and its constantly predicted death. One of the bigger problems these days, however, isn’t so much spammers as trolls and off-topic posters – typically school children (please, parents, confine your children to Myspace).
Spammers, at least, tend to post over a wide range of groups and hence can be killed off in one hit – and nobody tends to reply to their posts. Trolls, on the other hand, usually get a number of replies, which creates huge threads that hide legitimate topics. Worse are the off-topic political posters, who post to a number of only vaguely-related groups at the same time.
You can’t simply kill-file the original poster, because many other people reply, often even misguided regular posters. Kill-filing the whole thread on Subject header is also futile, because the trolls will soon start a new topic.
The best way I’ve found to handle these situations is to automatically kill threads started by known trolls. Unfortunately, no newsreader that I’ve seen seems to handle this situation, so I’ve written a script to take care of it for me. It’s a little situation specific, however – it relies on having a local spool (I use leafnode to suck down articles from remote news servers) and using nn. It’s written in perl, so it shouldn’t be hard to modify it to talk remotely, and to use other newsreaders’ kill file formats.