What is a proxy server

The word proxy means “acting on behalf of someone else,” and a proxy server acts on behalf of the user. A proxy server (or proxy for short) is any computer that carries out data traffic between networks or different transmission protocols. This computer is an intermediate server that physically separates end-user clients from the target computer on which they are searching for information. Depending on the application, company guidelines or application, proxy servers offer different levels of security, functionality and data protection.

When using a proxy server, the traffic on the way from the client to the web server runs through the proxy. The information on the request is then returned to the client via the same proxy server. However, there are exceptions to this rule. The server forwards the data received from the website to the user.

Modern proxy servers do much more than just forward web requests. They monitor data security and network performance. These servers act as firewalls and web filters, provide shared network connections and cache data in order to speed up frequent requests. A good proxy server protects users and the internal network from the bad things that try to infiltrate foreign networks from the Internet. In addition, proxy servers can offer a high level of privacy.

What is a Circuit Level Proxy?

The generic proxy (also circuit level proxy) has a specific filter algorithm. The proxy can act as a firewall and block certain IP addresses or ports for data traffic. You don’t even need to analyze data. Unlike its relative, the dedicated proxy, the generic proxy does not manipulate or save data. According to the 7-layer OSI model, it operates on the 3rd and 4th layers, where the filtering of addresses and ports takes place.


Protects addresses from disclosure: With proxies at the management level, there is no direct connection between an application client and an application server. Proxy servers hide the network’s address structure and make it difficult to access confidential information.

Provides a high degree of flexibility: as new Internet services are added, proxies automatically support them. Also, configuring clients to work with proxies is much easier than application-level proxies. Instead of reconfiguring each desktop application, a client desktop only needs to be configured once.

Enables comprehensive logging: System administrators can log and analyze all incoming and outgoing data traffic on a LAN.


Requires client software: Client computers must be configured so that all TCP / IP data is transmitted through the gateway at the line level.

Does not provide application-level security: Because the servers have no knowledge of the underlying application protocol, they cannot control application-specific information as tightly as an application-level gateway.

How does a proxy server work?

A proxy server (also called a dedicated proxy) is a utility that mediates requests between a client and a server using the HTT protocol. When we speak of a proxy today, we mean the proxy server in all cases. A proxy acts as an intermediary in the data traffic between client and server. The requests sent by the client are forwarded by the proxy server to the target server. The information is also sent back via the proxy.

It is possible for a proxy server to analyze the communication and change its content. The target server does not know the identity of the client if the traffic goes through a proxy server. A well-working proxy can manipulate communication between client and server. A proxy can also temporarily store data on its own server, for example to reduce processing time. In addition to the HTTP protocol, HTTPS, SMTP and FTP protocols are also used as protocols for data transmission.

What is a forward proxy?

According to ELECTRONICSMATTER, a forward proxy server sits between the client and an external network. It evaluates the outgoing requests and, if necessary, takes action before the request is forwarded to the external resource.

Most of the proxy services we will encounter on the internet are forward proxies. Virtual private networks and web content filters are both examples of forward proxies.

What is a reverse proxy?

A reverse proxy server resides between a network and several other internal resources. A large website can have dozens of servers sharing requests from a single domain. To achieve this, client requests are directed to a machine that acts as a load balancer. Depending on the workload, the load balancer then forwards the data traffic to the individual servers. Reverse proxies act as a cache memory and as a firewall to improve network security. The most popular open source reverse proxies include Varnish and Squid.

Not all proxies work the same

It is important for the operator of a proxy server to know which functions such a server offers in order to ensure that the server is suitable for the application.

Transparent proxy

A transparent proxy tells websites that the request is from a proxy server. It forwards the IP address of the user in order to identify him on the web server. Companies, public libraries, and schools often use transparent proxies for content filtering: they are easy to set up on both the client and server side.

Anonymous proxy

An anonymous proxy identifies itself as a proxy, but does not reveal the user’s IP address to the website. This helps prevent identity theft and keep the user’s browsing habits private. Anonymous servers can also prevent a website from delivering targeted marketing content to users based on their location. Browsing anonymously can prevent a website from using some ad targeting techniques, but it is not a complete guarantee.

Tasks of a proxy

Proxy are used in many areas. More and more private users are also using a proxy server, especially for data protection. The tasks of a proxy include the following:

Protection on the server side

If a proxy is used on the server side, it can serve to protect the server. This means that clients can only reach the target server via a proxy. Likewise, the proxy is the first point of contact for attackers who want to hack a website.

Protection of the user

There is a particular risk to data protection when using public networks. By acting as an interface between public and private networks, the proxy mitigates the consequences. A user does not send the data packets directly to the target server, but to the proxy, which forwards the packets. In return, the proxy can control which packets are sent back to the client in response and can therefore control communication.

Anonymous surfing

By using a proxy, the client programs are able to remain practically anonymous on the Internet. The identity and the real IP address of the user remain largely anonymous. Software such as the Tor browser are used to ensure privacy and data protection. Such anonymization services can be used, for example, to reach web servers that have been blocked for a network via the address of the service.

Bypass geoblocking

Sometimes entire websites or certain content are blocked due to the location of the user. In this case one speaks of geoblocking. A proxy server can then be used to access this content.

Data analysis and logging

Unlike a gateway, for example, a proxy server can log, save and analyze data. A statistical evaluation of the server data can also serve to improve performance.

What is a proxy server