The philosophy behind a Zero Trust Model assumes that there are attackers both within and outside of the network, so no users or machines should be getting accessed automatically without being trusted.
Another principle of zero-trust security is least-privilege access. This means giving users only as much access as they need, like an army general giving soldiers information on a need-to-know basis. This minimizes each user’s exposure to sensitive parts of the network. This further minimizes the attack surface of the network.
