We'll create fresh WordPress site with WPMU Block Spam By Math installed. You have 20 minutes to test the plugin after that site we'll be deleted.
This plugin protects your WPMU signup process against spambots with a simple math question. This plugin is based on the Block-Spam-By-Math plugin created by Alexander Grau. This only protects the new blog creation process and the new user creation process. If you wish to have individual blog protection use the regular Block-Spam-By-Math plugin on individual blogs.
For additional help check the plugin page at: http://www.jamespegram.com/wpmu-block-spam-by-math/