The definition of zero trust is a security model based on the premise that no one is blindly trusted and allowed to access company assets until they have been validated as legitimate and authorized. It supports the implementation of ‘least privilege access’, which is designed to selectively grant access to only the resources that users or groups of users require, nothing more. Additionally, those who are granted access to the network, data, and other assets are continuously required to authenticate their identity.
The benefits of zero trust have become increasingly more relevant in response to the rapid rise of mobile and remote workers, the bring your own devices (BYOD) trend, shadow IT, and the rapid rise of cloud services. While these trends benefited users and brought new levels of flexibility to IT, they also reduced the ability of the organization to control and secure access to data and network resources. This security model brings this control back, tightening up security in the face of a dissolving network perimeter.
Think of your network and data infrastructure as a building full of rooms with locked doors and each lock has its own individual key and you only grant users access only to the room with assets that they need and nothing else.

Blog: ゼロ・トラストの始め方
White Paper: Zero Trust Leading Practice