Is it possible to track a users ip address who using proxy website?
+4
A:
Some proxy servers add a X-Forwarded-For header to proxied requests.
Don't expect it to be always there and it may even contain false and/or invalid information, so it is not 100% reliable.
andri
2009-05-19 06:04:02
x-forwarded-for can also be used in legit scenarios. Beware of counting on this.
Ian Suttle
2009-05-19 06:21:51
+2
A:
Sometimes the proxy will add the Header: X-Forwarded-For, but that is sporadic at best.
JensenDied
2009-05-19 06:04:09
A:
Apart from HTTP_VIA, HTTP_FORWARDED, HTTP_X_FORWARDED_FOR, additional guess could be made if REMOTE_HOST or HTTP_USER_AGENT contains the word "via", "squid", "proxy", "cache" or "delegate". An anonymous proxy would likely hide these things.
eed3si9n
2009-05-19 06:20:45
+3
A:
Yes it is possible for proxy websites which is what you are asking (sites like anonymizer.com)
It is not possible with proxy gateways since proxies intercept all client requests and then in turn relay that, so by design you cannot determine the IP of the originator. This is what the other responses are alluding to.
However, the way proxy websites work is to convert all links of the form resource.aspx to proxy.com?resource.aspx. This means that if you have AJAX requests you may be able to skip the proxy and have the client relay the request directly to the server there by getting the client IP. You could also use Adobe Flash to communicate directly with the client and bypass the website proxy.
aleemb
2009-05-19 06:20:47
Challenge here is that very often client IPs are private network addresses e.g. 10.* and 192.168.* addresses. I'd be very cautious to rely on such data being unique.
stephbu
2009-05-19 06:25:48
@stephbu, this is regarding proxy websites, not proxy gateways so that doesn't apply.
aleemb
2009-05-19 06:32:14