Perimeter protection encompasses the security measures deployed at the boundary between an organisation's internal network and external, untrusted networks such as the internet. Traditional perimeter defences include firewalls, intrusion detection and prevention systems (IDS/IPS), demilitarised zones (DMZs), web application firewalls (WAFs), and email security gateways that filter traffic before it reaches internal systems.
While perimeter protection remains important, the shift towards cloud computing, remote work, and zero-trust architectures has fundamentally changed how organisations approach boundary security. Modern perimeter strategies combine traditional network-edge controls with identity-based access decisions, encrypted traffic inspection, and micro-segmentation to address the reality that the network perimeter is no longer a single, well-defined boundary.