CISSP Practice Test

CISSP practice test: what's covered

• Security Architecture & Engineering

Free CISSP sample questions

1. During a design review, an engineer proposes that if the authentication service becomes unreachable, the door controllers should automatically unlock to avoid trapping staff. The security architect insists on the opposite default for a high-security vault. Which principle is the architect applying?

   • A. Fail-secure, where a failure drives the system into a deny-by-default protected state
   • B. Fail-open availability, ensuring uninterrupted access during outages
   • C. Economy of mechanism, minimizing the controller's logic
   • D. Complete mediation, rechecking access on every request
   Show answer

   Correct: A. Fail-secure (fail-closed) means that when a component fails, the system defaults to a protected state such as access denied, which is correct for a high-security vault. Fail-open is incorrect because it prioritizes availability over confidentiality and would leave the vault exposed. Economy of mechanism is about design simplicity, not failure behavior, and complete mediation concerns rechecking authorization, so neither matches the scenario.

2. A team is reviewing a sprawling authorization module with thousands of conditional branches that no one fully understands. Citing Saltzer and Schroeder, the lead recommends rewriting it to be as small and simple as possible. Which design principle drives this recommendation?

   • A. Economy of mechanism, keeping designs small and simple to ease review and shrink attack surface
   • B. Open design, removing reliance on secret algorithms
   • C. Defense in depth, layering independent controls
   • D. Psychological acceptability, easing the user burden
   Show answer

   Correct: A. Economy of mechanism states that simpler, smaller designs have fewer flaws and are far easier to analyze and test. Open design is incorrect because it addresses secrecy of the mechanism, not its complexity. Defense in depth concerns layering controls, and psychological acceptability concerns usability, so neither addresses simplifying a complex module to reduce errors.

3. An auditor finds that an application caches a user's authorization decision at login and never rechecks it, so a revoked privilege still works until logout. To remediate this, the architect mandates that authority be verified on every access attempt. Which principle is being enforced?

   • A. Complete mediation, validating authority for every access to every object every time
   • B. Least privilege, granting only minimum required permissions
   • C. Separation of duties, splitting sensitive tasks across roles
   • D. Secure defaults, shipping the most restrictive configuration
   Show answer

   Correct: A. Complete mediation requires that every access be checked against current authority rather than relying on cached decisions, which directly fixes the stale-privilege flaw. Least privilege limits how much access a subject holds but not when it is rechecked. Separation of duties divides tasks among people, and secure defaults concern initial configuration, so neither addresses the caching problem described.

4. A vendor markets its product as secure because attackers cannot see its proprietary, undocumented encryption algorithm. A CISSP advising the buyer warns that this reasoning is fundamentally flawed. Which secure design principle is the vendor violating?

   • A. Open design, where security must not depend on the secrecy of the mechanism, only of the keys
   • B. Least common mechanism, minimizing shared resources
   • C. Fail-secure, defaulting to a protected state
   • D. Complete mediation, checking every access
   Show answer

   Correct: A. Open design (Kerckhoffs's principle) holds that a system's security should rest on protected keys, not on hiding the algorithm, because secrecy of mechanism is brittle and fails once reverse-engineered. Least common mechanism is about shared resources, fail-secure is about failure behavior, and complete mediation is about rechecking access, so none of those describes relying on a secret algorithm.

5. A security team is operationalizing least privilege after finding a help-desk account holding domain administrator rights it never needs. Which actions are faithful applications of the least privilege principle? (Choose TWO)

   • A. Grant each role only the minimum permissions required for its assigned tasks
   • B. Use just-in-time elevation so admin rights are temporary and time-bounded
   • C. Give every technician permanent domain administrator rights for convenience
   • D. Disable all auditing so permission changes are not recorded anywhere
   • E. Share one highly privileged account across the entire help-desk team
   Show answer

   Correct: A and B. Least privilege means granting only the minimum permissions a role needs and limiting elevated rights to when they are actually required, so minimal grants and just-in-time elevation are correct. Permanent domain admin for everyone, disabling auditing, and sharing one privileged account all expand standing privilege and reduce accountability, so they violate the principle and are incorrect.

Last updated: 2026-10-19

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