Use simple blacklists and whitelists to control who can and cannot register on your blog.
"Restrict Registration" is a plugin for WordPress that allows you to control who is registering on your blog. This plugin uses simple blacklists and whitelists to define who can register for your blog, and who is restricted. Use simple literal matching, flexible asterisk wildcard matching, or powerful regular expression matching: it's your choice! The options page is clear and easy to use. Set your lists, and you're done!
This plugin was inspired by WP-Deadbolt, but has been completely rewritten and redesigned, and several new features have been added.