Robert Peake

Obfuscation of email via the <code>[email]...[/email]</code> shortcode syntax using built-in <a href="https://codex.wordpress.org/Function_Reference/antispambot#Examples" rel="nofollow ugc">WordPress Codex</a> functionality.
Alternative variations:
<ul>
<li><code>[email]user@example.com?subject=foo+bar&body=baz[/email]</code> creates a mailto: link with subject and body pre-populated</li>
<li><code>[email nolink=1]user@example.com[/email]</code> just displays the email without a link wrapping it</li>
<li><code>[email linktext="click here"]user@example.com[/email]</code> displays the text “click here” with a link to the email address</li>
</ul>

Anti-Spambot

Obfuscation of email via the [email]...[/email] shortcode syntax using built-in Wordpress Codex functionality.

WP Chill

Silkalns

Cristian Raiber

A very useful plugin for everyone using WordPress. Adds reCaptcha security to the WordPress login form, register form and comment form. This plugin could help your blog get rid of a lot of spam comments or brute-force attacks.
Nothing gets passed it if the reCaptcha doesn’t validate.
A few notes about the plugin:
<ul>
<li>Supports audio or image captcha types</li>
<li>Can generate the reCaptcha image / audio type in a number of predefined languages</li>
<li>Adds reCaptcha protection to the WordPress login form</li>
<li>Adds reCaptcha protection to the WordPress register form</li>
<li>Adds reCaptcha protection to the WordPress comment form</li>
<li>Adds reCaptcha protection to the WordPress recover password form</li>
</ul>

Uber reCaptcha

This plugin adds the reCaptcha form to the WordPress login form, recover password form, register form and comment form.

Anti-Spambot vs Uber reCaptcha