What is a Screened Subnet in terms of cybersecurity?

A screened subnet, also known as a demilitarized zone (DMZ), is a network security architecture that is used to protect a network by segregating it from the public Internet.

The basic idea behind a screened subnet is to create a buffer zone between the internal network and the external network (the Internet) using two firewalls or other security devices. The first firewall, which faces the Internet, is configured to allow only traffic that is explicitly permitted by network administrators. This firewall is typically known as the external firewall.

The second firewall, known as the internal firewall, is located between the DMZ and the internal network. It is designed to allow traffic only from the DMZ into the internal network that is specifically authorized, and to block all other traffic.

The DMZ itself is a separate network segment that contains servers and other resources that are accessible from both the internal and external networks. These servers are typically web servers, email servers, or other servers that need to be publicly accessible.

By using a screened subnet, organizations can improve the security of their networks by isolating sensitive resources from the public Internet and limiting access to these resources through carefully controlled access points. The DMZ also provides an additional layer of defense against external attacks, by separating public-facing servers from the rest of the internal network.