I had been searching for a long long time for scripts that major sites have installed to prevent form spamming - those "enter the code" you see in image types. Finally I found it and installed on my sites, phew! The problem actually was the keyword to use to search for such scripts. After much browsing, I found that they are called "Captcha Scripts". Although there are not much free good ones, the one that impressed me most was at : http://www.phpcaptcha.org/ It's pretty simple to use (with little programming knowledge of course) but your web host should be able to support the features used by it.