Perimeter

In cybersecurity, a perimeter refers to a defined boundary or edge around an IT system or network that separates it from the untrusted external environment.

The purpose of a perimeter is to provide a first line of defense against unauthorized access, malware, and other security threats. The perimeter is typically secured using a combination of technologies such as firewalls, intrusion detection systems, and access control mechanisms.

The concept of a perimeter is based on the idea of a castle or fortress, with a clearly defined boundary that separates the inside from the outside. However, with the growth of cloud computing and the increasing use of mobile devices, the traditional perimeter-based approach to security is becoming less effective, as more data and systems are moving outside the boundary.

Zero trust architecture as defined by NIST actively discourages against the traditional perimeter-defense.