wppal

Easy Captcha is an ideal solution for those who want to try different types of captcha to achieve an optimal site usability and captcha protection ratio. It allows a WordPress site owner to choose which captcha should be used on a particular page.
Currently the plugin supports 3 types of captcha:
<ul>
<li>Hidden captcha, </li>
<li>Simple image captcha,</li>
<li>Google reCaptcha</li>
</ul>
Hidden Captcha is invisible to site visitors and does not assume any specific user actions. It just checks that a visitor behaves like a human. Although it might seem that Hidden Captcha does not fully correspond to the definition of CAPTCHA (found at the end of the FAQ), it still distinguishes a human from a bot based on natural human behavior. Hidden Captcha also allows checking whether a visitor’s browser has JavaScript and Cookies enabled.
Simple Captcha works in a traditional manner: it shows an image and requires a user to enter a captcha code. Simple Captcha stores captcha values on the server side using a custom session approach.
reCaptcha is a reliable and powerful captcha service provided by Google for free. Please visit <a href="http://google.com/recaptcha" rel="nofollow ugc">reCaptcha site</a> for more details
Any type of captcha from above may be added to the following WordPress site places:
<ul>
<li>Comment forms,</li>
<li>Login page,</li>
<li>Registration page,</li>
<li>Password reset page. </li>
</ul>
With Easy Captcha you can easily install different types of captcha on each individual page.
Please read the FAQ and Installation sections for more details.

Easy Captcha

Several types of captcha to protect your site in one easy to use plugin.

ThreatPress

<a href="https://www.google.com/recaptcha/intro/invisible.html" rel="nofollow ugc">Google reCAPTCHA</a> is designed to protect your WordPress site from spam bots. This plugin integrates <a href="https://www.google.com/recaptcha/intro/invisible.html" rel="nofollow ugc">the new Invisible reCAPTCHA</a> into your WordPress site.
What is protected with Invisible reCaptcha?
WordPress 
* Login form 
* Registration form 
* Comments form 
* Forgot password form
WooCommerce 
* Login form 
* Registration form 
* Lost password form 
* Reset password form 
* Product review form

Google Invisible reCaptcha by ThreatPress

A simple plugin to integrate the new Invisible reCAPTCHA into your WordPress site.

Easy Captcha vs Google Invisible reCaptcha by ThreatPress