A security model that trusts no user or device by default, checking identity and permission on every request to every resource.
Zero Trust Architecture is an enterprise cybersecurity philosophy predicated on the principle: "Never trust, always verify."
Older perimeter security, the "castle and moat" model, trusted whatever was already inside the network. Zero Trust assumes an attacker may already be inside, so every request has to prove who is asking and from which device, wherever it comes from.
Zero Trust is a baseline requirement for securing distributed data architectures and preventing data exfiltration when deploying internal AI systems.
See also Data Exfiltration, Air-Gapped Environment and Role-Based Access Control.