Least privilege is the principle that every user, process, and system should hold only the permissions needed to do its job, and nothing beyond that. A help desk technician can reset passwords without touching payroll, and a backup service can read files without any right to delete them.
The payoff is a smaller attack surface. When an account with narrow rights is compromised, the intruder inherits only those narrow rights and cannot immediately reach sensitive systems. The tradeoff is administrative effort, since tightly scoped access needs regular review as roles change. A classic failure is privilege creep, where people accumulate rights across years of transfers and promotions while nobody ever removes the old ones. It is one of the oldest ideas in security precisely because it keeps paying off.
How is least privilege tested on the CISSP?
Least privilege is a cornerstone of Domain 5, Identity and Access Management, and it underpins how you design accounts, roles, and administrative access. Exam scenarios often describe excessive permissions and ask which principle was violated, so learn to spot access that exceeds the task. Review Domain 5: Identity and Access Management.
NIST defines the term in its cybersecurity glossary.