How it works:
Basic mode works by analyzing the information your browser sends when it makes a web request (the "headers" and requesting IP address). Every web page you visit has access to this information. Parts of it, in particular the requesting IP address, the "User-Agent" header and the "Referer" (sic) header, are typically retained in that web server's log.
Advanced mode performs a more active analysis. In advanced mode, your browser is put through situations that do not normally occur and the behavior examined. Additionally, some tests are "active" - which means that our webserver may reach out and touch your requesting IP address back when you connect to us. Some of the advanced tests are purely informational - the meaning of the results is up for interpretation.
(Hah! I know I am using a proxy, but you don't show it!)
Some proxy servers ("Anonymous" proxies) are configured to conceal their presence. We do attempt to reveal as much about them as we can, but if they do their job well we will not detect their presence. If the proxy you are using does not show up on the "Basic" check it can be reasonably assumed that other websites will not detect it either.
(I am not using a proxy, but you found one!)
Your computer may be going through some sort of proxy without your knowledge. This is sometimes done at the ISP level or by the IT department at your workplace. Alternatively, some viruses and other malicious programs redirect your traffic for their own nefarious purposes. We can show you where we think your traffic is coming from, but we can not tell you for sure which, if any, of these scenarios is true.
(You found a possible proxy?)
Some of our tests results aren't black and white. If we have found indicators but no proof that your connection is being proxied you will get this message.
(I found a proxy! Is that bad?)
(I didn't find a proxy! Is that good?)
We are unable to answer that question. Whether a proxy configuration is good or bad is really defined by the environment. HTTP proxies are used to cache content over low bandwidth links, to filter content, to provide anonymity, to log usage, or any other thing that could be accomplished by snooping in, caching or interfering with connection between your computer and the world wide web. They have both legitimate and illegitimate uses.
(Hey, I found this sweet free proxy on the Internet that your tests didn't detect!)
Be careful. There are many reasons that people might be running an open proxy:
In general, it is a good idea to consider any communication you partake in over the Internet as "being watched". When you are using a proxy server, even though the destination web server may not know your identity - you may be being watched twice. Protect yourself. Consider your actions and level of trust carefully.
You've got my location wrong!
Meh. Geolocation is voodoo and really shouldn't be trusted in any event. At best, we won't have any better data than MaxMind's Creative Commons data set: http://www.maxmind.com.
(I have an idea for a new test!)
Contact us! If possible we would like to add it.