Nik's Technology Blog

Travels through programming, networks, and computers

Contact forms, SPAM relay email and the CAPTCHA

Back in January this year I decided enough-was-enough with increasing amounts of automated SPAM coming into my inbox and originating from my site. I decided to do something about it. My contact form has been attracting lots of SPAM bots which were trying their best to relay their SPAM through my site.

My form has always had the To: and From: fields hard-coded however, so I doubt anything ever got relayed, but they all got sent to me anyhow.

As a result I now verify that the form was actually filled in my a HUMAN each time the form gets sent! I've built an ASP CAPTCHA function to achieve this (Completely Automated Public Turing test to tell Computers and Humans Apart), more about CAPTCHAs here.

Accessibility and CAPTCHAs

There are however down-sides to this SPAM free existence. CAPTCHA images in the form that I am using are inherently inaccessible, so I intend to use another system in conjunction with my image CAPTCHA as used my Matt Cutts on his blog.