Proxy server is a computer that sits between a client computer and the Internet, and provide indirect network services to a client. It may reside on the user's local computer, or at various points between the user's computer and destination servers on the Internet. A proxy server intercepts all client requests, and provide responses from its cache or forwards the request to the real server. A client computer is connected to the proxy server, which acknowledges client requests by providing the requested resource/data from either a specified server or the local cache memory. Client requests include files or any other resources available on various servers.

Types of Proxy servers

Proxy servers are classified into several types based on purpose and functionality. Some of the most common types and their uses can be described as below:

Web Proxy is the most common type of proxy application, which responds to the user requests by accessing resources from cached web pages and files available on remote web servers. This facilitates quick and reliable access to data for local network clients. If the requested resource is not found in the cache, then a web proxy fetches the file from the remote server, and saves a copy in the cache before returning it to the client.

Transparent Proxy is mostly used for caching websites and overcoming simple IP bans. However, such proxies do not provide any user anonymity since user’s original IP address is exposed. Transparent proxies are not specifically configured on the client computers.

Anonymous proxies do not hide the original IP address of the user; however, they provide adequate anonymity to most users. Anonymous proxies are easily detectable.

A distorting proxy, identifies itself as a proxy server, and modify the HTTP headers to disguise the original IP address.

Tunneling proxies are capable of passing client requests and return responses without making any modifications. These are also referred to as gateway proxies.

A forward proxy responds to client requests by retrieving data from a wide range of sources on the internet. It is also referred to as an Internet-facing proxy.

Open proxies belong to the category of forwarding proxy servers, which are accessible by any internet user since they can receive and return requests from any client computer. Meanwhile, anonymous open proxies are used for user anonymity to conceal the IP address.

Reverse proxies, also known as surrogates, usually receive requests from the Internet and forward them to internal network servers. A reverse proxy server forwards requests to one or more proxy servers, whose response is returned to the client computer, the user of which has no knowledge on the origin of the response.

Where is a Proxy server used?

Proxy servers are used for several purposes. If it is used as a caching web proxy, it can dramatically improve performance of a web response. When a request is made by a client, a caching proxy returns response directly from its cache if the document already exists. Otherwise, it makes the request to the real server, returns the result, and save it in its cache for later use.

Proxy servers are also used as "web proxies" to filter web page contents. An organization or company may use a proxy server to block offensive web contents from viewed by the users. Considering the growing need within organizations to prevent employees from accessing specific websites, such as facebook.com, proxy servers are being deployed across the computers connected to the intranet. Some web proxies are able to reformat web pages to suit a specific set of audience, or cater certain organizational or personal internet usage purposes. Further, web proxies can be used to prevent the attack of computer viruses and malware, as well as other hostile content transferred across the internet web pages. However, users can also use web proxy servers to access those blocked sites indirectly. These web proxies are built with PHP or CGI to implement the proxying functionality, and provide web access to those sites blocked by corporation and school proxies. Moreover, Internet Service providers (ISPs) may also use proxies to block computer viruses and other offensive contents.

There are several advantages of Proxy servers. We intend to provide some of the most basic uses of proxy servers.

Performance Improvement:

Proxy servers also contribute to improved web performance since the results of the user requests are saved in cache memory for a set period of time. This is achieved with the help of a caching proxy server, which could save a large amount of time while catering to the requests from a vast user load. A caching proxy server maintains a local copy of frequently requested web content. Hence, it can accelerate service requests by retrieving content from the cache memory, if it had already been requested by another client on the same network. This feature contributes to a significant reduction in upstream bandwidth usage and costs for large organizations with thousands of employees.

Monitoring and Filtering User Requests:

As discussed earlier, web proxies can be used to filter user requests, and block certain content or web pages from being accessed. This can be achieved with the help of a content-filtering web proxy server that differentiates the users’ level of control over the content, based on the user type - Guest or Administrator.

Content-filtering proxies are generally used in organizations and educational institutions with strict internet-usage policies. Blocking certain websites, and restricting access to specific key words and censoring undesirable content are some of the basic features provided by content-filtering or web-filtering proxies. However, there are certain web proxies that are used to bypass geo-restrictions and censorship regulations by using certain advanced services that help access resources from blacklisted web locations.

Anonymous Browsing:

An anonymous proxy server is another type of web proxy that anonymizes users' online activities. This type of proxy server directs the user requests to a destination server, which ultimately has no knowledge of the source of the request. Only the proxy is aware of the source of the request, including the user IP address and location.

Advertisements targeting specific geographical regions Web Proxies can also be used to validate and verify geo-targeted advertisements. Servers of such ads validate the source IP address of the user request, and determine the geographic location of the request with the help of a geo-IP database. The user requests are responded via proxy servers that are located within the respective geographical location, to ensure that advertisements displayed are purely relevant to the users’ location.

Translation:

Considering the global audiences, translation proxies have been developed to localize/translate the content of a source website into a local language of the client computer. Responses for requests sent by local users are replaced with translated content from the source website, and passed back through the proxy server. Some translation proxies also provide additional services such as excluding source content or substituting source content with original local content.

Conclusion

The most popular proxy server used today is a Web Proxy, and it is used to filter contents and allow anonymous browsing. Being able to unblock geo-restricted content is also a wide used application for using public web proxies. Although proxies provide anonymous browsing and content filtering, they are mostly limited to web browsing and also lack security. For secure and encrypted communication with privacy protection, we recommend VPN solution.

If you have any questions about Proxy Server, please post your question on Proxy Server Forum.

Reference: Wikipedia