In Settings>>General>>Membership un-check “Anyone can register”
Also, you need 3 peices of spammer info in order to submit to anti-spam databases. username, email and IP. WP doesn’t log the new user IP, so if you install Register IP – MultiSite it will take care of that.
Here is a very handy tool for checking and submitting spammers http://www.gunnerinc.com/fslcinfo.htm
It will check against 14 databases and submit to 2 (SFS and BotScout) it also has a very fast batch submitter.
Just do a search in your add new plugin page for Stop Spammer Registrations Plugin.
Or got to the authors site http://www.blogseye.com
That should fix you right up! 🙂
