prevent multipe submitts

[dfr574]

Hello,

I have a form where a user submits his or her email address and a short message.

How would you prevent that person from submitting multiple times?

I'm using a MySQL data base so I have already thought about checking if that email address has been entered. But's what's from stopping someone from useing a fake email address.

I thought about logging there IP, but what if multiple users are connecting from the same LAN useing NAT?

Any idea's?

Thanks

[aaron_karp]

IP checking might be a good idea nonetheless, and take the risk of losing those users with identical IPs.

Or, you could use cookies which will be stored on individual machines.

How about a three pronged approach?

1) Check Email Address
2) Check Cookies
3) Check IP

If their IP exists in your database, but their email address doesn't and they don't have a cookie, then your chances are probably very good that it's a unique user on a LAN, so you can process their submission.

[dfr574]

Those are some excellent idea's.

Thanks.