I'm running this awards site that distinguishes unique votes via IP addresses. I need to know if there's a way you can prevent people from voting who are on proxies.

Or if there's a certain way you can detect if the IP they're voting from is a proxy.

Thanks.

You can check for the HTTP headers "Via" or "X-Forwarded-For", but not all proxy servers add these headers.

Unfortunately there isn't any really way to tell if some one is using a proxy or if its a legitimate vote especially if there using a proxy such as Tor where they could use thousands of IP addresses very easily. The way around this would be to set up a log in page, e-mail verification or browser cookies.