CISSP Practice Question: A security architect is considering secure design…

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

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  Single point of failure

  Why it's wrong here

  A single point of failure (SPOF) represents a component whose failure would cause the entire system to stop functioning. While avoiding SPOFs is a critical objective in resilient system design, particularly for availability, it is not considered a fundamental secure design principle in the same vein as defense-in-depth strategies like layered security or least privilege. Instead, it's a characteristic to mitigate through redundancy and fault tolerance, which are themselves enabled by other design principles.

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  Layered security

  Why this is correct

  Layered security, also known as defense-in-depth, is a fundamental secure design principle that involves deploying multiple, independent security controls throughout a system. This approach ensures that if one security control fails or is bypassed, other controls are still in place to detect and prevent unauthorized access or actions. It significantly increases the attacker's effort and time required to compromise a system, making it a cornerstone of robust cybersecurity architectures.

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  Open design

  Why it's wrong here

  Open design, often associated with Kerckhoffs's Principle, suggests that the security of a system should not depend on the secrecy of its design or implementation, but rather on the secrecy of its keys or passwords. While a valuable principle promoting scrutiny and robustness through transparency, it is not considered an essential secure design principle for implementing defense-in-depth itself. Defense-in-depth primarily focuses on the deployment of multiple, diverse controls, irrespective of whether their internal workings are public or private.

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  Fail safe

  Why it's wrong here

  The fail-safe principle dictates that when a system component fails, it should do so in a way that minimizes harm or exposure, typically by denying access or reverting to a secure state. While crucial for system integrity and availability, and often implemented as part of a secure system, it is not as universally fundamental to the concept of defense-in-depth as layered security or least privilege. Defense-in-depth focuses on preventing breaches through multiple barriers, whereas fail-safe primarily addresses the system's behavior after a failure has occurred.

• ✓

  Least privilege

  Why this is correct

  The principle of least privilege mandates that users, programs, or processes should be granted only the minimum necessary permissions to perform their legitimate functions. This significantly reduces the attack surface and limits the potential damage an attacker can inflict if a system or account is compromised. By restricting capabilities, least privilege is a critical component of defense-in-depth, ensuring that even if one layer is breached, the scope of the compromise is contained.

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