Identifying proxy

[Raymond]

Is there a service out there that can check if an IP is a proxy?

[SEOMike]

Anonymous proxy servers hide your IP address and thereby prevent unauthorized access to your computer through the Internet. They do not provide anyone with your IP address and effectively hide any information about you and your reading interests. Besides that, they don't even let anyone know that you are surfing through a proxy server. So, I don't think that there is currently any way to discover if a user is visiting through a proxy.

[Manish Singh]

Do a telnet on the standard proxy ports to check if the IP is proxy.

Ports
8080
8000
6588
3128

Proxies generally run on these ports. It is not a 100% effective way of finding whether the IP is a proxy but it works most of the times :-)

[teodorul]

Why do you want to identify proxies?

If you are looking for fraud evidences on your logs you might use the method that Manish Singh described.

You must know that a proffesional frauder will use non standard ports proxyes, and proxy servers are not online 24h/day, this could be a limitation of the method descibed by Manish.

Look for proxy ranges on google, 90% of the public proxyes come from those ranges, for the rest use the other method.

I would add other ports :
80
3382
2301