What is a DMZ Network? A DMZ or demilitarized zone is a perimeter network that protects and adds an extra layer of security to an organization’s internal local-area network from untrusted traffic. The end goal of a demilitarized zone network is to allow an organization to access untrusted networks, such as the internet, while ensuring its private network or LAN remains secure. Organizations typically store external-facing services and resources, as well as servers for the Domain Name System (DNS), File Transfer Protocol (FTP), mail, proxy, Voice over Internet Protocol (VoIP), and web servers, in the DMZ.

How Does a DMZ Network Work? Businesses with a public website that customers use must make their web server accessible to the internet. To protect the corporate local area network, the web server is installed on a separate computer from internal resources. The DMZ enables communication between protected business resources, like internal databases, and qualified traffic from the Internet. A DMZ network provides a buffer between the internet and an organization’s private network. The DMZ is isolated by a security gateway, such as a firewall, that filters traffic between the DMZ and a LAN. The default DMZ server is protected by another security gateway that filters traffic coming in from external networks.

It is ideally located between two firewalls, and the DMZ firewall setup ensures incoming network packets are observed by a firewall—or other security tools—before they make it through to the servers hosted in the DMZ. This means that even if a sophisticated attacker is able to get past the first firewall, they must also access the hardened services in the DMZ before they can do damage to a business. If an attacker is able to penetrate the external firewall and compromise a system in the DMZ, they then also have to get past an internal firewall before gaining access to sensitive corporate data. A highly skilled bad actor may well be able to breach a secure DMZ, but the resources within it should sound alarms that provide plenty of warning that a breach is in progress.