How Does DMZ Work?

In this tutorial, we are going to see How does DMZ work? Firewall systems allow defining access rules between two networks. However, in practice, companies usually have several sub-networks with different security policies. This is why it is necessary to set up firewall architectures to isolate the different networks of the company: This is called “network partitioning”.
 

 

How Does DMZ Work?

When specific machines on the internal network need to be accessible from the outside (web server, mail server, public FTP server, etc.), it is often necessary to create a new interface to a separate network that can be accessed from both the internal and external networks, without compromising the company’s security. The term “demilitarized zone” (DMZ) is used to designate this isolated zone hosting applications that are available to the public. The DMZ acts as a “buffer zone” between the network to be protected and the unfriendly network.
 

^{Image source: https://commons.wikimedia.org/wiki/File%3ADMZ_network_diagram_2_firewall.svg}
 
 
The servers located in the DMZ are called “bastions” because of their position as the front end of the company’s network.

The security policy implemented on the DMZ is generally as follows:

• Traffic from the external network to the DMZ allowed;
• Traffic from the external network to the internal network is not allowed;
• Traffic from the internal network to the DMZ allowed;
• Traffic from internal network to external network allowed;
• Traffic from the DMZ to the internal network is not allowed;
• Traffic from the DMZ to the external network is not allowed.

TheDMZ, therefore, has an intermediate level of security, but its level of security is not sufficient to store critical data for the company.

It should be noted that it is possible to set up internal DMZs in order to partition the internal network according to different levels of protection and thus avoid intrusions from the inside.
 
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