Protect your guestbooks and feedback forms. Stop all automated registrations and spam postings through your web site’s forms.
Captcha, image verification code, is an essential security test which is carried out on the completion of a web form, which serves to determine whether the user is human or a spam bot.
Spam bots are created by programmers to search the internet for webforms to send spam. Unfortunately programmers create bots/programs that can submit forms, crack passwords and gather email addresses from millions of websites by following the links within a page.
No spam-bot/program (i.e. non-human) can read a line of jumbled letters and numbers from an image, as long as the letters and numbers are not all the same size and font. Because of this, the Image Verification security method guarantees that only human users can physically submit a form.