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Protect your forms from spam with hard to break and easy to read Secure CAPTCHA images from <a href="http://www.securecaptcha.net/" rel="nofollow ugc">SecureCAPTCHA.net</a>.
Secure CAPTCHA allows to distinguish between form submition made by human and script (robot, bot, program etc.). 
It gives you ability to reject all form submitions made in automatic way. 
Secure CAPTCHA was designed to be both hard to break with a script and easy to solve by the humans.
Most of available simple CAPTCHA libraries are easy to break. 
They use one font and scale or rotate each letter individually. 
There are scripts on the web that are capable to break them. 
Some CAPTCHAs add random lines and patterns, but it make the text harder to read by a human.
Secure CAPTCHA is made with handwriting. 
Letters are connected together and it is difficult for a script to split text into individual letters. 
Moreover, each letter looks somewhat differently depending on it’s two neighbour letters. 
And finally, the whole text is transformed with some randomly chosen nonlinear transformation.
Many CAPTCHA implementations on the web are really hard to read. 
Sometimes it is even impossible. 
Secure CAPTCHA is easy to solve for a human: our images have big letters and high contrast between the text and the background.

Secure CAPTCHA

Protect your forms from spam with hard to break and easy to read Secure CAPTCHA images from SecureCAPTCHA.net.

yaCAPTCHA is a CAPTCHA plugin for WordPress that helps you block comment spam 
from automated bots. In order to post comments, users will have to write down 
the characters that are part of an image. Since it is relatively hard for 
automated programs to figure out those characters, this will help prevent 
comment spam from those programs.
<h4>Requirements</h4>
<ul>
<li>WordPress 1.5 or higher.</li>
<li>PHP 4.1.0 or higher with GD2 library support.</li>
<li>Theme must support the ‘comment_form’ action.</li>
<li>PHP sessions enabled and properly configured.</li>
</ul>
In case you are wondering, most hosting providers should have those basic 
requirements in place.
<h4>Strengths vs other solutions</h4>
<ul>
<li>Easy to install</li>
<li>Does not require Javascript to work</li>
<li>Broad WordPress version support</li>
</ul>
<h3>Thanks</h3>
Thanks to Kruglov Sergei for creating KCAPTCHA, his pretty good CAPTCHA. You 
can visit KCAPTCHA website <a href="http://www.captcha.ru/en/kcaptcha/" title="KCAPTCHA
website">here</a>.

yaCAPTCHA

yaCAPTCHA is a CAPTCHA plugin for WordPress that helps you block comment spam from automated bots.

Secure CAPTCHA vs yaCAPTCHA