dannyx

This is my first WordPress plugin that i made it for personal use and to learn how to build plugins. 
This plugin replaces the submit button on the post comment section with a set of buttons from images. 
A small message provides the user a hint on what button to use to submit the comment. 
Demo: http://www.arcweb.ro/blog/2011/12/21/testing-cutecaptcha-plugin/
Requirements: 
PHP mcrypt should be available on the server, i will add more encryption methods if required. 
Session support is optional, supports caching of post pages without session but with lower security.
Customize: 
All the information and parameters to configure are in cutecaptcha.php 
The images and messages can be customized and should be quite fun to adapt it with the 
subject of each website, especially expecting that anybody that wants to post a comment 
should have a good idea about that subject.
Security: 
The variety in images and messages will make it difficult for automated bots to break it. 
The plugin is intended for a regular blog that will never attract dedicated spamers. 
At this moment the association between messages and photos can be analyzed, but it is possible to add 
another layer of protection if required. I strongly suggest that each site uses personalized images and 
messages related to their content.
TODO: 
Alternative encryption functions for servers without php mcrypt. 
Extra layer of security on images: Raw data inserted in file, modified with 
variable watermarks for each session. 
Display a specific number of buttons from a gallery of buttons. 
IP Block: block ip’s after a number of failed submits for a number of days.

Cute Captcha

Replaces the submit button  with a set of buttons from a set of images. A small message provides the user a hint on what button to use.

pluginkollektiv

Few users are familiar with the comment block list built into WordPress. Located in the WordPress admin area under “Settings”—“Discussion”, that block list for incoming comments accepts values (words) to identify spam by.
Additionally to plugins like <a href="https://wordpress.org/plugins/antispam-bee/" rel="ugc">Antispam Bee</a> in order to fight spam successfully a curated comment block list is recommendable. You can either update the list manually, or utilize a very detailed global <a href="https://github.com/splorp/wordpress-comment-blacklist" rel="nofollow ugc">comment block list</a> that gets updated on a regular basis.
Block List Updater has been developed to keep your comment block list in your WordPress installation up to speed with the curated global list on GitHub.
The plugin will check the global comment block list on GitHub multiple times a day. Whenever new anti-spam values have been added to the global list, Block List Updater will read the global list and update your WordPress database accordingly. While the check-up process will run several times a day, the plugin will only update the database when it detects an actual change of the global comment block list on GitHub.
<h3>Support</h3>
<ul>
<li>Community support via the <a href="https://wordpress.org/support/plugin/blacklist-updater" rel="ugc">support forums on wordpress.org</a></li>
<li>We don’t handle support via e-mail, Twitter, GitHub issues etc.</li>
</ul>
<h3>Contribute</h3>
<ul>
<li>Active development of this plugin is handled <a href="https://github.com/pluginkollektiv/blacklist-updater" rel="nofollow ugc">on GitHub</a>.</li>
<li>Pull requests for documented bugs are highly appreciated.</li>
<li>If you think you’ve found a bug (e.g. you’re experiencing unexpected behavior), please post at the <a href="https://wordpress.org/support/plugin/blacklist-updater" rel="ugc">support forums</a> first.</li>
<li>If you want to help us translate this plugin you can do so <a href="https://translate.wordpress.org/projects/wp-plugins/blacklist-updater" rel="nofollow ugc">on WordPress Translate</a>.</li>
</ul>
<h3>Credits</h3>
<ul>
<li>Author: <a href="https://sergejmueller.github.io/" rel="nofollow ugc">Sergej Müller</a></li>
<li>Maintainers: <a href="https://pluginkollektiv.org/" rel="nofollow ugc">pluginkollektiv</a></li>
</ul>

Block List Updater

Automatic updating of the comment block list in WordPress with antispam keys from GitHub.

Cute Captcha vs Block List Updater