Principle of least authority

In information security, computer science, and other fields, the principle of least privilege (also known as the principle of minimal privilege or the principle of least authority) requires that in a particular abstraction layer of a computing environment, every module (such as a process, a user, or a program, depending on the subject) must be able to access only the information and resources that are necessary for its legitimate purpose.

The principle means giving a user account only those privileges which are essential to perform its intended function. For example, a user account for the sole purpose of creating backups does not need to install software: hence, it has rights only to run backup and backup-related applications. Any other privileges, such as installing new software, are blocked. The principle applies also to a personal computer user who usually does work in a normal user account, and opens a privileged, password protected account (that is, a superuser) only when the situation absolutely demands it.

When applied to users, the terms least user access or least-privileged user account (LUA) are also used, referring to the concept that all user accounts at all times should run with as few privileges as possible, and also launch applications with as few privileges as possible.

The principle of least privilege is widely recognized as an important design consideration in enhancing the protection of data and functionality from faults (fault tolerance) and malicious behavior (computer security).

Benefits of the principle include:

In practice, there exist multiple competing definitions of true least privilege. As program complexity increases at an exponential rate, so do the number of potential issues, rendering a predictive approach impractical. Examples include the values of variables it may process, addresses it will need, or the precise time such things will be required. Object capability systems allow, for instance, deferring granting a single-use privilege until the time when it will be used. Currently, the closest practical approach is to eliminate privileges that can be manually evaluated as unnecessary. The resulting set of privileges typically exceeds the true minimum required privileges for the process.

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