CAPTCHA is a trademark of Carnegie Mellon University. This document describes a similar technology that is available for free.
I implemented a contact form on my new site recently, and would you believe that I was receiving lots of spam through it very quickly indeed! The site had hardly been indexed by the search engines before this happened.
I tried implementing a weak human test of my own – one of those things where you input a code that is presented to you as a graphic to prove that you are human, but this was attacked very easily indeed, and I was still receiving the spam.
I was amazed when I read of the technology that has been developed to get around the human test. (CAPTCHA is a mnemonic that stands for Completely Automated Public Turing test to tell Computers and Humans Apart. It is designed to stop automated systems filling in scripts protected by it on the web. For some background on Turing tests, visit Wikipedia here.) I realised that optical character recognition could conceivably be used to defeat most CAPTCHA systems, and some really sophisticated software has been developed to do this. It is even available to the public.
I could not spend days refining my own solution. After a little bit of research, I came across puremango, a free visual confirmation PHP CAPTCHA script. It’s very easy to integrate with your web site; I had it up and running within an hour or so! Since I installed that script, the spam has stopped. I’m still getting mail from humans through the contact form, which is what it’s there for.
David Thomas, The Affiliate Marketer
