A plugin for stopping most spambots from registering user accounts on WordPress sites with open user registration. This plugin creates a simple, hidden field that spambots will automatically fill out. If this registration field has data entered into it, the registration process is cut off and no spam user account will be created.
This plugin isn't an end-all solution to spam registrations. It's a simple solution for one type of spam registration issue that has come in handy for me many times.
There's no configuration. Simply install, activate, and let the plugin do its work.