Many people wonder, what is a proxy server? A proxy server can have different applications, but it literally means when another computer makes requests from your computer to a server computer. You might want to use proxy servers in different situations, or you might be using one without even realizing it.
Proxy Web servers.
One of the most common applications for a proxy server is in Web applications. A proxy server retrieves Web site data you request from the server and saves a copy of it to the local proxy cache. The next time you request the Web site, the proxy server pulls the cached copy from the local cache instead of going all the way to the server for the data. ISPs may use proxy Web servers to reduce server requests and save resources.
Proxy servers for filtering.
Another common application for proxy servers, especially in a hosted server context, is Web filtering. A proxy server may be configured to filter offensive content, filter spyware or dangerous programs or simply filter spam. In this case, the proxy server stands between your computer and the server and blocks content specifically designated by the proxy server as dangerous or against server programming.
PHP and CGI.
PHP and CGI are specific protocols that proxy servers can use to access Web sites. These are basically gateway sites that enable users to access other Web sites through them. You might use a CGI proxy to access sites that are otherwise blocked by corporate or school proxies, or a CGI proxy might serve as a gateway between your computer and another computer.
Proxy servers that mask IP addresses.
In some cases, proxy servers can actually mask or hide your IP address and grant you relative anonymity on the Web. If you want to hide your unique IP address when you're surfing the Web, you have four server solutions in the form of proxy services that specifically affect IP addresses: transparent proxies, anonymous proxies, distorting proxies and high anonymity proxies.
Transparent Proxy: A transparent proxy tells the server computer that it's a proxy. Your IP address is available through http headers. Transparent proxies aren't really designed for anonymity on the Web; they're primarily intended to cache Web site content.
Anonymous Proxy: Anonymous proxies are the next step up in terms of IP address protection. Unlike transparent proxies, anonymous proxies hide your IP address. The server still knows it's dealing with a proxy instead of directly with a computer, but your IP address stays hidden.
Distorting Proxy: A distorting proxy also tells the server that it's a proxy, but it sends false IP address information through http headers. A server may think a distorting proxy is actually a transparent proxy and that it's getting correct IP address information; it has no way to verify that the IP information is incorrect. This is an option if you want to hide your IP address but let the computer think you're not hiding it.
High Anonymity Proxy: These proxies offer the ultimate protection. They don't tell the server computer that they are proxies, and they don't disclose your original IP address. The server has no way of knowing that it's not dealing directly with a computer instead of a proxy, but your IP address is completely protected.
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