Least privilege means granting only the minimum access necessary to perform an authorized task.
Least privilege reduces blast radius by limiting accounts, roles, and services to only the permissions they need, only for the time they need them. It is a key control for both humans and service identities.
The principle that a security architecture should be designed so that each system entity is granted the minimum system resources and authorizations that the entity needs to do its work. (Compare: economy of mechanism, least trust.)
Tutorial: This principle tends to limit damage that can be caused by an accident, error, or unauthorized act. This principle also tends to reduce complexity and promote modularity, which can make certification easier and more effective. This principle is similar to the principle of protocol layering, wherein each layer provides specific, limited communication services, and the functions in one layer are independent of those in other layers.