A proxy server is a computer that offers a computer network service to allow clients to make indirect network connections to other network services. A client connects to the proxy server, then requests a connection, file, or other resource available on a different server. The proxy provides the resource either by connecting to the specified server or by serving it from a cache. In some cases, the proxy may alter the client’s request or the server’s response for various purposes.

Web proxy servers are generally classified into four groups: Transparent, Anonymous, Distorting, and High Anonymity. Transparent proxies identify themselves as a proxy server and also makes the original IP address available through the http headers. Anonymous proxies identify themselves as a proxy server but does not disclose the original IP address. Distorting proxies identify themselves as a proxy server, but make an incorrect original IP address available through the http headers. High Anonymity proxies do not identify themselves are proxy servers and do not reveal the original IP address.

When it comes to security the bottom line is to be wary when using proxy servers, and only use proxy servers of known integrity (e.g., the owner is known and trusted, has a clear privacy policy, etc.), and never use proxy servers of unknown integrity. If there is no choice but to use unknown proxy servers, do not pass any private information (unless it is properly encrypted) through the proxy.

If you are in the habit of using proxy servers and are unsure of their type you can visit whatismyipaddress.com and try the proxy tester to see if your proxy server is detectable.