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.

alexmoskovsky

Provided by <a href="http://multitoolbox.com/" rel="nofollow ugc">Multitoolbox</a>.
Simple, but strong captcha, built to prevent spam in WordPress comments. Succesfully blocks Xrumer-like tools.
To leave a comment on your blog, visitors need to simple check the captcha’s field. That’s all! Forget about annoying typeing of letters and digits.
Features:
<ul>
<li>Extremely simple passing for human;</li>
<li>Built-in id’s and function name’s generator to produce unique and random values, Xrumer won’t pass;</li>
<li>Catchy look, you commentators won’t miss;</li>
<li>Captcha’s code will be pasted into the comment form via JavaScript, so spam-bots will get a big parsing problems; </li>
<li>Comment text saving, so if commentators forgot to check captcha’s field, they never have to write commen again.</li>
</ul>
Languages:
<ul>
<li>English;</li>
<li>Русский;</li>
<li>Український (thanks to <a href="http://sweatego.ru/" rel="nofollow ugc">Sweat Tony</a>);</li>
<li>Italiano (thanks to <a href="http://sweatego.ru/" rel="nofollow ugc">Sweat Tony</a>).</li>
<li>Čeština (thanks to <a href="http://spa-ostrov.ru/" rel="nofollow ugc">Zeleny Rajce</a>).</li>
<li>Français (thanks to <a href="http://www.android-software.fr/" rel="nofollow ugc">Laurent</a>).</li>
<li>Беларуская (thanks to <a href="http://pc.de/" rel="nofollow ugc">Marcis G.</a>).</li>
</ul>
Amcaptcha is bulletproof solution tested on many blogs.

Amcaptcha

Simple, but strong captcha, built to prevent spam in Wordpress comments. One-click solution tested on many blogs!

Math Quiz vs Amcaptcha