I don't know about viri, but http://akismet.com/ is the tool of choice for automated spam detection in websites. It's not perfect of course, but quite popular and accurate.

We used akismet here for a while but it blocked a few valid posts occasionally. Nowadays I prefer just disabling anonymous comments and moderating the few spam posts that we sometimes get by registered members. I'm also planning to add an open "guest" account for anonymous members who don't yet want to register but would like to comment on a certain story.

We do use a spam module on Libervis and Nuxified though and it blocked a few (and on Libervis quite a few) spam posts, so that's another good option for drupal based sites.

Cheers

Thanks guys, will look into akismet and see how to reduce false flags, assuming I can delta the api...

Seems like a service web hosts would offer by default. Maybe a server side p2p app (s2s?) could allow blacklist/pattern sharing among trusted website operators and the option of subscribing to a central list, come to think of it the p2p aspect would be a fine facility in Thunderbird too for anti-spirus. Am I losing the run of myself here?

No I think that makes quite good sense. Actually, isn't akismet in a way p2p already? It gathers data from various websites and puts it into its system, so yeah, it pretty much seems to be that, except that it's a bit more centralized perhaps.