In computer networks, a proxy server is a server used for forwarding requests of clients to a remote server. The proxy server works like a gateway between the client and the internet[1]: the client will send the request to the proxy server; the proxy server sends it to the actual remote server and gets the response; then the proxy server sends the response to the client.
Proxy servers are named this way because they act like a proxy(an agent or substitute) of the client computer.
There are many benefits of using a proxy server. First, the client machine can exchange data with the remote server without making a direct connection. This way, the client's real internet address will not be known to the remote server. This is sometimes called anonymizing because it makes the client anonymous A second advantage is that when the proxy server is itself able to serve the request made by the client, it will not contact the remote server any more. So the load on the remote server will be reduced by using a proxy server.[2] This type of proxy servers are called caching servers.
Big organizations (or even countries) sometimes use proxy servers to control access to the Internet. A large bank may use a proxy server that only allows connections to other websites relevant to banking. The proxy server might however block access to Websites offering free email or serving pornographic material. It might also block access to file sharing applications. Limiting access to specific content on the internet is also called internet filtering.[3]
A proxy server may have one or more of the functions described below:
A caching proxy server can service requests from clients, without contacting the remote server; instead, it sends the data which it has stored from a previous request. This is called caching.
Caching proxy servers reduce the work load of the remote server. However, they have their own problems, especially if they are not configured well. Some problems are described in RFC 3143.
A web proxy is a proxy server that focuses on the traffic over the World Wide Web. It may be used to block offensive web content, or to control access of clients to online content. They may be used by schools, corporations or countries.
Web proxies can also be used to track how different individuals have used internet access.
An anonymizing proxy server removes identifying information from the clients' requests, for the purpose of anonymity. They may also be used to break through filtered contents on the internet.
A proxy server is called an open proxy if every one can connect to it and use it. Usually, open proxies are proxy servers which are badly configured.[4] Open proxies may be abused easily; for example, a bad user may send a corrupting request to a remote server, but hide himself behind an open proxy, so the administrators of the remote server cannot stop him. Open proxies can also be used for spamming.[5] For this reason, some websites do not allow connections to their web servers through known open proxies.