Thanks Luis for mentioning Bad Behaviour: all the information about it on mediawiki.org was wrong (it was described as an AbuseFilter-like thing) so I had never looked into it before. You're the first person mentioning success with it, but it's possible we only hear from unhappy MediaWiki users which have problems with spam, not from those who solved the problem. :)

I've updated the extension's page (and others): https://www.mediawiki.org/wiki/Extension:Bad_Behavior I see two issues: 1) they don't say anywhere if patterns for IP, HTTP headers etc. are shared and checked on a central location (like Akismet does IIRC) or kept local; 2) it's probably impossible to use it on Labs given this problem with cache and privacy, though it may be useful for sites without caching or with less strict privacy policies. http://redmine.ioerror.us/issues/41

Nemo