Stop Spam with reCAPTCHA

CAPTCHAs (Completely Automated Public Turing test to tell Computers and Humans Apart) can protect you and your users from spammers and crackers.
Broadly spoken, user don’t like this ugly looking pictures and I saw a lot of false implemented code or very easy to crack. To see some examples which CAPTCHAs can be broken you should check out http://sam.zoy.org/pwntcha/

An easy to implement, free and I guess secure service can be found on recaptcha.org and you help by digitizing books.

You go there, create an account, generate a API key and include the code into your application form. After 10 minutes you have a nice secure solution.

I’ve been using it now for some months and I’m very happy with it.
An important point to me was that recaptcha has audio support, so visually handicapped people also can login.

On the site you can find example code and plugins for many programming languages and well known applications.

http://recaptcha.net
http://recaptcha.net/plugins/php/
Breaking a Visual CAPTCHA
http://sam.zoy.org/pwntcha/