atitan

Math Quiz generates dynamic math problem in the comment form to beat spam robots and supports flexible form style customization.
Demo website: https://atifans.net/ (with Supercache and AJAX comment form enabled)
For PayPal donation, please use this email address: info a.t atifans.net
Features:
<ul>
<li>Dynamic problems prevent spam robots from posting unwanted content.</li>
<li>Quiz form inserted using AJAX for better compatibility with HTML cache plugins.</li>
<li>Form style and position can be customized in the control panel.</li>
<li>Trackbacks and Pingbacks are checked with DNS queries to avoid abuse.</li>
<li>Optional login page protection.</li>
</ul>
Translators:
<ul>
<li>SLV-es (Spanish)</li>
<li>Joao Paulo (Portuguese)</li>
</ul>

Math Quiz

Math Quiz generates dynamic math problem in the comment form to beat spam robots.

Peter

Stop a lot of spambots from polluting your site by making visitors identify a random word displayed as an image before commenting and optionally before registering. You can customize the pool of words to display.
<h4>Features</h4>
<ul>
<li>
Toggle whether registered users need to enter the word
</li>
<li>
Random font display
</li>
<li>
No cookies required
</li>
<li>
No JavaScript required
</li>
<li>
Auto-generated audio for visually impaired users
</li>
<li>
Easy-to-read
</li>
<li>
No mapping of words from the code — words are used once or removed after 24 hours
</li>
<li>
Reminder of what was entered if you get the word wrong
</li>
<li>
Selective blocking of trackbacks, pingbacks
</li>
<li>
Easy to translate
</li>
<li>
Compatible with caching plugins
</li>
</ul>
<h4>Negatives</h4>
<ul>
<li>
Purposely no obscuring techniques so that the anti-spam word is easy to read
</li>
<li>
The more people who use this plugin, the more motivation for spambots to target it
</li>
</ul>
<h4>Requirements</h4>
<ul>
<li>
GD Library and FreeType Library (There’s a diagnostic page to tell you whether you have them installed. If needed, just ask your web host to install them!)
</li>
<li>
WordPress 3.2 or higher
</li>
</ul>
<h4>Translations</h4>
<ul>
<li>ru_RU translation by koc</li>
<li>sk_SK translation by Patrik Žec (PATWIST) of http://patwist.com</li>
</ul>

Peter’s Custom Anti-Spam

Stop a lot of spambots from polluting your site by making visitors identify a custom word displayed as an image before commenting.

Math Quiz vs Peter’s Custom Anti-Spam