Most effective form of CAPTCHA?

Question

Of all the forms of CAPTCHA available, which one is the \"least crackable\" while remaining fairly human readable?

Answer 1

CAPTCHAS, I believe should start being considered heavily when designing the UX. They're slow, cumbersome, and a very poor user experience. They are useful, don't get me wrong but perhaps you should look into designing a honeypot.

A honeypot is created by adding a hiddenfield at the bottom of the form. Because spam bots will fill in all the fields on the page blindly you can do a check:

If honeypotfield <> Empty Then
   "No Spam TY"
Else 
    //Proceed with the form 
End If

This works until there is a specifically designed spambot for your site, so they can choose to fill out selected input fields.

For more information: http://haacked.com/archive/2007/09/11/honeypot-captcha.aspx/