Any chance to detect if the person is behind a proxy?

hi all,

I know this is pretty impossible, but wh knows if there's any chance to do that and block access?  Also , how do you guys ban the person you don't really want to see on your site, I mean except IP & cookies, what else can be more reliable solution, can it be something like Wiindows unique certificate or something like that, I saw a lot of Request ServerVariables functions, any  of them can be unique or not for each user?

Also I know that php has function to detect the whole host not just an IP address, is that possible with asp?

Thanks,
N_F_S
N_F_SAsked:
Who is Participating?
 
vnvkCommented:
I believe its not possible in ASP.

even for PHP, I tried the function at the below url:

http://www.phpbuddy.com/article.php?id=22

and it failed. Cos, I am behind a proxy server and a firewall and that url displayed the ip address of our ISP, as well as dsplayed that we are not behind proxy.

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Starr DuskkASP.NET VB.NET DeveloperCommented:
in below examples, if it comes up blank, you know they are not behind a proxy...

ASP with Proxy detection

<%
    ipaddress = Request.ServerVariables("HTTP_X_FORWARDED_FOR")
    if ipaddress = "" then
        ipaddress = Request.ServerVariables("REMOTE_ADDR")
    end if
%>
 


PHP with Proxy detection

<?
    if (getenv(HTTP_X_FORWARDED_FOR)) {
        $ipaddress = getenv(HTTP_X_FORWARDED_FOR);
    } else {
        $ipaddress = getenv(REMOTE_ADDR);
    }
?>
 
JSP with Proxy detection

<%
    if (request.getHeader("HTTP_X_FORWARDED_FOR") == null) {
        String ipaddress = request.getRemoteAddr();
    } else {
        String ipaddress = request.getHeader("HTTP_X_FORWARDED_FOR");
    }
%>

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