ReCaptcha
“ReCaptcha reduce anomalous requests from hitting your website or specific URLs”
The ReCaptcha functionality enables you to distinguish between human and automated access to websites. You can set a captcha for the whole website or per single source IP, or enable it only for some specific URLs. ReCaptcha will never interrupt users and is intended to run automatically when users load pages or click buttons, therefore it’s a smooth way to enable your default defenses.