Spam Protection with Captchas

Most of all webmasters, which have contact forms, registration forms or online polls on their websites, know the problem: in a short time they are receiving spam. The reason is, that spammers are using so-called harvesters (also known as webcrawler, spider, robot, or bot). This is a special software, which is searching automatically through the WWW, analyzes websites and tries to fill out any discovered forms with spam.

With Captchas (Completely Automated Public Turing test to tell Computers and Humans Apart), a method, which is able to distinguish between a computer (bot) and a human, it is possible to prevent these spam in most cases.

Examples and Downloads: (PHP, inclusive source code)

Captcha (CSS) - Spam protection with CSS captcha
Captcha (Graphic) - Spam protection with graphic captcha
Captcha (Text) - Spam protection with text captcha
Captchamania - New captcha technologies
Complete example - Graphic-Captcha to protect a form against spam