Effective plugin with responsive support

This plugin is certainly effective at stopping spam account registrations and the plugin creators very quick to respond to support requests and issue updates. By its own admission, it inevitably sometimes blocks genuine user registrations but there are various configuration options for site admins to try to get the right balance. For a site with a fairly low number of registrations, I found it manageable to occasionally need to manually override the blocking of genuine users in return for blocking a lot of spam registrations.