Although we use a captcha (Extension:ConfirmEdit#ReCaptcha .28NoCaptcha.29, saying "Effectiveness at stopping spam" = High), we still get sometimes a bunch of new spam-users registered at our wiki. Just 1 time in 2 months or so, then 10 to 15 new users, and for some users a page or two about cigarettes, Vietnamese literature, college and so on. And then it stops. We block the users and remove the pages but we want them to not be created at all.
I don't understand how these users are created, must be manually.
Anybody any suggestions how to solve this?