security//Zero Trust

Zero Trust is a security model in which no user, device or service is trusted because of where it sits on the network, and every request to a resource is authenticated, authorized and checked against policy on its own, and it replaces the older *castle and moat* design in which everything inside the corporate network was trusted by default. The idea was named at Forrester around 2010 and formalised by NIST in SP 800-207 (2020); its slogan is *never trust, always verify*.

Zero Trust is a security model in which no user, device or service is trusted because of where it sits on the network, and every request to a resource is authenticated, authorized and checked against policy on its own, and it replaces the older castle and moat design in which everything inside the corporate network was trusted by default. The idea was named at Forrester around 2010 and formalised by NIST in SP 800-207 (2020); its slogan is never trust, always verify.

The motive is that the perimeter stopped existing. Staff work from home, services run in several clouds, contractors and machines connect from everywhere, and once an attacker is inside a flat network (one phished laptop is enough) a perimeter model lets them reach almost anything, which is how lateral movement turns a small breach into a large one. Zero Trust assumes the attacker may already be inside and makes each step costly.

In practice it rests on a few mechanisms working together:

Strong identity for everything. Users authenticate with multiple factors, devices prove they are managed and patched, services carry their own credentials, and every access decision starts from that identity (authentication, IAM).

Least privilege, per request. Each identity gets only the access its task needs, for as long as it needs it, and the decision is re-evaluated with context such as device health and location (minimum privilege).

Segmentation. Resources are split into small zones so that reaching one does not open the others, with encrypted connections even inside the data center.

Continuous monitoring. Every access is logged and analysed, so unusual patterns surface quickly (SIEM).

Zero Trust moves the security boundary from the network to each request. Being on the right network grants nothing; being the right identity, on a healthy device, asking for something that identity is allowed to do right now, is what grants access.

It is an architecture: vendors sell pieces of it, and adopting it is years of work on identity, inventory and policy. In plants and grids it meets OT, where old controllers cannot authenticate anything, so Zero Trust ideas are applied at the gateways and network zones around them (cyber-physical security, defense in depth).