Perimeter security vs Zero Trust

Why they differ

Perimeter security trusts whatever is inside the network; Zero Trust trusts nothing by location alone and checks every request.

Perimeter security

Fundamentals

Guarding the edge between an organisation's own network and the outside world, and trusting what is already inside.

Formal

A security model that places its main controls, such as a firewall and VPN, at the border of the internal network. Traffic is checked on the way in or out, while users and machines inside the border are largely trusted by default.

In plain English

A castle with thick walls and one guarded gate - once you are past the gate, you can walk into almost any room.

In practice

A municipality lets every office PC reach every server freely because they all sit behind the firewall, so one infected laptop brought in by an employee can reach the payroll system.

Why it matters

With cloud services and remote work there is no longer one clear edge to guard, and an attacker who gets inside meets little resistance.

Zero Trust

Controls & technical basics

A security principle of never trusting anyone automatically - every request is checked, even from inside the network.

Formal

A design approach in which no user, device or network location is trusted by default; each request for access is checked for identity, device health and need, and given only the least access required for that one task.

In plain English

Like a hospital where your badge is checked at every ward door, not just at the main entrance - getting inside the building does not get you everywhere.

In practice

An employee at her desk inside a ministry opens the payroll system and is still asked to prove who she is, while her laptop is checked for current updates before the page loads.

Why it matters

Once one machine inside is taken over, a network that trusts its insiders lets the attacker roam freely; checking every request limits how far one break-in spreads.

Shared connections

Defence in depth