Least-privilege is a security principle that gives each account, service, or tool only the access it needs to do its job, and nothing more. If a backup script needs read access, it should not also have permission to delete files or change admin settings. The same rule applies to human users, APIs, cloud roles, and AI agents.
This matters because stolen credentials and compromised automation often become far more dangerous when they can move freely across systems. Attackers look for overprivileged accounts to reach email, cloud consoles, source code, or sensitive data, then escalate impact quickly. Defenders use least-privilege with role-based access control, just-in-time permissions, approval gates, and regular access reviews. In AI-heavy environments, it is one of the main controls that limits what an autonomous tool can touch if it behaves unexpectedly or is manipulated by an attacker.