Cleanfeed

Through the late 1990s, Usenet anti-spam work mostly meant cancelbots: the junk propagated around the world first and was hunted down second. Jeremy Nixon wrote Cleanfeed as a hook into INN's Perl filter, inspecting every incoming article before it reached the spool. It hashed message bodies and rejected the same text posted to too many groups, binaries dumped into text groups, and known spam patterns.

The difference was that a filtered article was never passed on to neighbouring servers. Spam control became something any news admin could run locally, without waiting for NoCeM or someone else's cancel run. The name was later reused by British Telecom for an entirely unrelated blocking system, to the lasting confusion of search engines.