ImHuman provides more humane, fun, easy, secure and mostly user friendly captcha (are you really a human?) detection for posting comments.
Create customizable contact forms and sticky contact button for your WordPress blog. Web 2.0 style.
figlet math challenge, captcha replacement, based on TryMath php class and phpFiglet
Photo Captcha with user defined images to reduce the spambot prize/payload to one website at a time. A captcha with "Which one of these things is not
Pictcha is a very unique & secure CAPTCHA.
Adds a CAPTCHA to account registration that uses Vidoop's ImageShield.
A script which protects the comment form from spam. Does four ways of protection.
Let admin create a page to do automatic exchange links with other webmaster
Security Captcha es un sistema para prevenir spam de cualquier tito, tanto por personas como por scripts creados por personas.
Add a captcha to protect comments from being spammed using Cryptographp library.