OSpam-a-not is the easiest way to protect your site from spam.
OSpam-a-not uses two unobtrusive techniques to protect your forms from a flood of spam.
First, OSpam-a-not uses a Time Gate. This is a hidden timestamp that records how long it took to fill in a form. If the form was submitted more quickly than humanly possible, we can block the submission.
Second, OSpam-a-not uses a Honey Pot. A text field is added to the form and hidden by adding a style tag at the end of the document head tag. It isn't visible to a human user, but a spambot doesn't see that and fills in the field anyway. If we find anything at all in that field when the form is submitted, we've caught a spambot in the honey pot! And the form is blocked.