How do I prevent automated form submission?

How would you prevent an automated form submit so that only people from the form page can submit a form?

The problem with automated form submission is that some keep spamming.

 

how about adding a captcha to your form?

 

Yep, some kind of image verification will sort em out!

 

Captcha + referrer checking, making sure the submitted stuff actually came from your form page. Though the latter can easily be spoofed, but with a session ID or captcha verification it's pretty tight.

 

Don't use referrer checking since users can disable this and I think that norton (firewall) does this automatically.

You can either use a captcha, or after the person submits the form make them click on another button before it gets sent to you/inserted in the db. The automated programs likely won't know that.

 

Seems a good combination, I put a confirm button and give users the last chance for editing what they have entered on the form.

 

this is one class has captcha feauture: http://www.phpclasses.org/formsgeneration