Thread:Project:Support desk/Media Wiki is a spam machine unless it is set up properly./reply (12)

...which can be used with Extension:AbuseFilter. However, that is advanced - compared to just using the extensions provided with the tarball. The easiest solution is deactivating registration and making registration compulsory for editing. That is two lines in LocalSettings.php - and the installer even offers you to set them with a single click (I think the option was called "closed wiki").