This plugin by Xrvel simply reCAPTCHA to your login form. By adding reCAPTCHA to your login form, you can prevent bots, scripts, etc from trying to login to your WordPress website.
You must have reCAPTCHA account to use this plugin. It is free at http://recaptcha.net/ WP-reCAPTCHA plugin needs to be installed first.
Plugin Homepage: http://www.xrvel.com/336/programming/wordpress-login-recaptcha-plugin