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Security Fundamentals & Crypto · Foundational

Security Perimeter

The boundary separating trusted components from untrusted ones, either within a system or around a network.

Definition

In system architecture, the security perimeter separates the TCB from untrusted components. In network security, it traditionally refers to the boundary between internal networks and external ones, enforced by firewalls and gateways. Cloud and remote work have eroded the network perimeter, driving adoption of zero trust.

Example

The firewall between the corporate LAN and the internet defines the traditional network perimeter.

Exam tip

Zero trust assumes the perimeter is not a reliable trust boundary.

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