A system must validate access rights to all its resources and must not rely on a cached permission matrix. If the access level to a given resource is revoked but is not reflected in the permission mat

Question

Options

• Aeconomy of mechanism
• Bcomplete mediation
• Cseparation of privilege
• Dleast common mechanism

• B
  92% (22)
• C
  4% (1)
• D
  4% (1)

Explanation

Complete mediation (Option B) is correct because this principle requires that every access request to every resource must be validated each time it occurs, rather than relying on cached or previously stored permission data. If a system uses a stale permission matrix, it risks granting access to users whose rights have been revoked - a direct violation of complete mediation.

Why the distractors are wrong:

• Economy of mechanism (A) refers to keeping security designs simple and small to reduce potential vulnerabilities - unrelated to real-time permission checking.
• Separation of privilege (C) means requiring multiple conditions or approvals before granting access, like two-factor authentication - not about cache validation.
• Least common mechanism (D) advises minimizing shared resources or mechanisms between users to reduce risk - again, unrelated to caching permissions.

Memory tip: Think of "complete mediation" as a bouncer who checks your ID every single time you try to enter - no wristbands, no memory of seeing you before, no shortcuts. If your access is revoked, you're stopped immediately because nothing is cached or assumed.

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