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proxy Server

Basics: Whole purpose of a proxy server

A proxy server serves as a representative for requests from a client or for requests to a web server and forwards them. In addition, a proxy server has a wide range of tasks thanks to its deputy role.

Visible and transparent proxy server

Essentially, a visible proxy server differs from a transparent proxy server in the network infrastructure. With a transparent proxy server, at least one communication partner cannot see that an additional instance (proxy) is available as a central communication bridge.

The communication partners assume that they communicate directly. The proxy server is therefore “invisible”. The network infrastructure is configured in such a way that all requests are automatically forwarded via a proxy entity. The proxy then acts as a representative as the communication partner.

 

A visible proxy server, on the other hand, appears as a visible, independent instance and is addressed via its own public IP address.

Areas of application for proxy servers:

acceleration

A cache acts as a temporary store that stores frequently used data for faster retrieval. Caching enables a proxy server to respond more quickly to regularly used data (e.g. websites) or repetitive requests. This saves bandwidth and shortens response times.

Save load distribution and bandwidth

In addition, a proxy server is able to control the bandwidth and load balancing. This is made possible by allocating bandwidth to clients and thus resources are optimally used. For example, the blocking of transmission capacity by one or more clients can be prevented. If there are several lines or interfaces, the proxy ensures that the load is distributed uniformly.

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filtering

Proxy servers offer network administrators the option of actively filtering and controlling local data traffic. For example, certain websites can be blocked or influenced through the use of white and black lists. The local users behind the proxy are therefore not granted access to these websites. When accessing a blocked website, you may be redirected to the fact that the requested website is not available.

concealment

The client sends a request to the proxy server. This processes the request and forwards it to the router with the IP address of the proxy server. Ultimately, the request is passed from the router to the Internet. The actual IP address of the client is not published and the origin of the client can be partially disguised.

Forward proxy (client protection)

In this case, a proxy server is implemented between a local area network (LAN) and the Internet. Local end devices can thus be protected from the public network. All outgoing requests are first sent to the proxy server, which accepts these requests and forwards them to the target computer on the Internet using its IP address (proxy IP address) as the sender.

The proxy server thus acts as a representative and also assumes a control function.

Reverse proxy (server protection)

Web servers can also be secured, for example against Denial of service attacks, by implementing a proxy server for access from the public network. Clients from the Internet therefore have no direct access to the target server. Inquiries are first received by the proxy, checked and forwarded to the server in the background if they are acceptable.

Application Level & Circuit Level

Application Level Proxy:

This type of proxy has certain functions that can analyze data packets. This procedure is therefore on the seventh layer (application layer) of the OSI model (Open System Interconnection). Therefore, this type of proxy server has the ability to block, modify and forward certain data packets according to pre-configured rules. An application-level proxy is also called an application or application filter.

Circuit level proxy:

The circuit level proxy works on the 3-4 layer (switching and transport layer) of the OSI model and is therefore not authorized to analyze packet data. This type of proxy is often used as a firewall filter module that allows data packets to be filtered through ports and IP addresses. He cannot influence the communication himself. The filtering is based on the ALL OR NOTHING principle. Data packets are either let through or blocked.

Proxy vs VPN

VPNs typically operate at layers 2-3 of the OSI model and redirect all your traffic, while proxy servers operate at layers 3, 4, and 7, depending on configuration, and only redirect traffic from a specific application or browser. VPNs can be slower than proxy servers because they additionally encrypt the data.

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