What is a Proxy Server?

A Proxy is in the context of computer networks and refers to a program or device that performs an action on behalf of someone else. Its most common purpose is a server used to allow Internet access to all computers in an organization when only a single computer or IP address is connected.

What is a Proxy Server?

What is a Proxy, How Does It Work, and What Are Its Types?

The term is used in computer networks when an agent makes sense. Its most common use is the server acting as a computer that disconnects a client’s network connections to the target server.

The most common of these usage types are Web Proxy servers. These prevent people from browsing certain web pages for several possible reasons such as security, performance, anonymity.

There are different structures for other protocols such as FTP. For example, Proxy-ARP can act as a router in the network as it acts as an intermediary between computers.

It can also be regarded as a design model that has the same scheme as the network proxy. A hardware component can act as an intermediary for others as well. It may be a person authorized to act on behalf of another person outside of calculation.

In short, although it is always synonymous with agent and agent, it has a very general meaning.


In general, there are many advantages to using a secure server on a network or for any other purpose.

You can limit and restrict the rights of users and only give permissions to the server. Therefore, only one of the users should be equipped to do the main work.

When several clients request the same resource, the server can cache this process and respond directly when another user requests this information. This way, the user does not need to reconnect to the target and the process is done faster.

The secure server can detect unauthorized clients by filtering and may not respond to their requests.

If all users are identified as one, it is difficult for the accessed resource to distinguish them. But this can be bad, for example when you need to do an identification.

Web page requests are made directly to the secure server, not to the Internet. Therefore, it eases the traffic on the network and reduces the load on target servers where fewer requests arrive.

It creates a cache that prevents the same information transfer between servers for a while to get the user a faster response.

It can cover a large number of users to request via web content. It can filter the pages according to the restriction criteria set by the administrator depending on the values ​​and properties that are not allowed and create a restriction when necessary.

Based on the same filtering function and called Privoxy, it has the purpose of protecting privacy on the Internet. It can be configured to block addresses and cookies and can change content on request.


There are also disadvantages to using a secure server. For example, some actions may not be followed because requests from many users must be answered.

Therefore, you need to control who has access to your services.

Between source and target, some users may not want to be filtered through the server. In this case, copies of the data received by the server cannot be accessed. Therefore, a user who cannot access the cache cannot access the newer version of the target resource.

In such a case, the server cannot verify the old and new data for the user requesting the data.

Proxy serving multiple users may cause direct communication problems between the sender and the receiver.

If the cache changed by the server since the last load, the pages viewed may be out of date.

A web designer might specify that browsers do not cache their pages in web content, but this method generally does not apply to a proxy server.

Accessing the Internet via a secure server rather than a direct connection is more difficult to configure as it prevents advanced operations over some ports or protocols.

Hiding pages and objects requested by users may be considered a violation of privacy for some people.

How Does It Work?

It allows other computers to connect to a network indirectly.

When a computer on the network wants to access information or a resource, it is actually a server that handles the communication and then transfers the result to the first computer.

This method can also be used in situations where direct communication is not possible. It can be used both for speed and security by providing indirect connections to inaccessible queries.


   Web Proxy

It is a server used for specific application access to the web.

Besides the general benefit of a secure server, it provides a cache for web pages and downloaded content shared by all computers on the network.

As a result, it eases the burden on Internet connections by improving access times for matching queries.

The working logic of secure web servers is as follows;

  1. The client makes a request for an Internet resource specified by a URL.
  2. When the cache server receives the request, it looks for the resulting URL in its local cache.
  3. It checks the date and time of the request page version with the remote server.
  4. If the page was not changed since it was loaded into the cache, it responds immediately. So it saves a lot of traffic as it only changes one package to check the version.
  5. If the version is outdated or not in the cache, it retrieves it from the remote server, sends it back to the client, and saves or updates a copy in its cache for future requests.

The cache usually uses an algorithm to determine when a document is out of date. Depending on the size of the document and its access history, it must be removed from the cache.

Two of these basic algorithms are LRU and LFU. Web-based Proxies can also filter the content of web pages served.

These servers can also be configured for some applications that try to block offensive web content.

It changes the format of web pages for a specific purpose or target audience. Proxy servers can also be used to block viruses and other offensive content served by some network operators, remote Web pages.

For example, an ISP’s client sends a request to Google that reaches the server that it originally owned, and that request does not go directly to the IP address of the Google domain.

This request is usually more demanded by a high group of users. So the ISP keeps it at its Proxy for a certain time and generates a response in a much shorter time.

When the user creates a search on Google, the secure server is no longer used and the ISP sends the request.

   Transparent Proxy

Many organizations use a proxy server to enforce network usage policies, maintain security, and create caching services.

Normally, a NAT or Web Proxy is not transparent to the client application.

Therefore, the user can escape from the server by changing the settings. One advantage of this is that it can be used for corporate networks.

A transparent server can be combined with NAT so that connections are routed without being configured and unaware by the client. This method is a variant used by ISPs.

   Reverse Proxy

It is a server installed at the address of one or more web servers. All traffic from the Internet to and from one of these web servers passes through the server.

There are several reasons to use this type:

  1. It is an additional layer of defense and therefore protects web servers.
  2. Usually, SSL encryption is not done by the web server itself, but by the server equipped with SSL acceleration hardware.
  3. It can distribute the load among several web servers. In this case, each web page may need to rewrite its URLs.
  4. It can download web servers by storing static content.

   NAT Proxy

Another method that provides service as an intermediary in a network is NAT. This service is also known as network address translation or IP masking.

It is a technique where the source or destination addresses of IP packets are rewritten. NAT is used when multiple users share a single Internet connection.

Within the Local Area Network (LAN), computers use IP addresses reserved for private use.

It is responsible for translating private IP addresses to a single public address and also for sending the requested documents to the user.

The use of private IP addresses is very common in companies and homes with a few networked computers and outside access to the Internet.

It provides a certain security for accessing the Internet via NAT. Thus, there is no direct link between the external and private network, and the computers are not directly attacked from the outside.

Thanks to NAT, it can be ensured to allow limited access from outside and direct requests to the server to a specific machine.

The NAT functionality is located in the firewall and is very useful because it does not need any special configuration that can only access the computers of the private network as if they were a router.

   Open Proxy

It is a type that accepts requests from any computer, whether connected to your network or not.

In this configuration, the server handles all requests from a computer that can connect to it as if it were a request from a server.

Therefore, this type of configuration allows it to be used as a gateway for the mass sending of spam emails.

It is used to store and redirect services such as DNS or Web browsing by caching requests, allowing users to process faster.

This usage is very useful, but it increases abuse by applying an open configuration to the whole Internet.

For example, many servers such as IRC or Email block access to these servers, often using blacklists.

   Cross-Domain Proxy

It is used by servers that have restrictions to communicate between items in different domains.

Ajax, for security reasons, only the web page making the request is allowed access to the same source domain.

If you need to access other services located in other domains, the Cross-Domain server is installed, which receives Ajax requests and forwards them to external domains.

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