As you may know the Joomla contact form is a target for spammers, so a common way to stop spammers from your joomla contact form is the well-knowed CAPTCHA. We have developed our Joomla Ajax Captcha plugin solution with this idea in mind, it must work without change any joomla core files and must be accessible. The attempts to verify that the user is in fact a human by requiring the user to read a distorted set of characters from a bitmapped image, then enter those characters into a form.This type of visual and textual verification comes at a huge price to users who are blind, visually impaired or dyslexic. The accessibilty is the main issue for the classic captcha, we have solved this problem serving a sound file (mp3) that can be listened to if the visual verification is not suitable for the user or adding a math question.
The advantages of our Captcha solution are: