CISSP Software Development Security Practice Question
A development team is designing a new application and wants to ensure that if a failure occurs, the system remains secure by default. Which design principle should they apply?
⚠ Common exam trap
Many candidates confuse fail-secure (secure on failure) with fail-safe/fail-open (available on failure) — CISSP often swaps these terms to test whether you know the security-vs-availability trade-off.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Fail-secure
Fail-secure is the design principle that dictates a system should default to a secure state when it fails — for example, denying access, locking doors, or dropping connections rather than allowing them. It directly addresses the requirement that 'if a failure occurs, the system remains secure by default.' The other principles address access scope, layered controls, and fraud prevention, not failure behavior.
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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Least privilege
Why it's wrong here
Least privilege is a fundamental security principle dictating that users, programs, or processes should be granted only the minimum necessary access rights to perform their legitimate functions. While crucial for reducing the attack surface and limiting potential damage from a compromise, this principle focuses on controlling access during normal operation and does not directly define the specific behavior or security state a system should adopt when a component fails or an error occurs.
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Defense in depth
Why it's wrong here
Defense in depth is a comprehensive security strategy that employs multiple, independent layers of security controls to protect assets and information. The aim is to create redundancy, ensuring that if one control fails or is bypassed, another layer will still be in place to provide protection. However, this architectural approach focuses on the overall resilience and layering of security mechanisms, rather than specifying the default security posture a single application or component should adopt upon an internal operational failure.
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Separation of duties
Why it's wrong here
Separation of duties is an organizational control designed to prevent a single individual from having complete control over a critical process, thereby significantly reducing the risk of fraud, error, or malicious activity. It mandates that tasks requiring high trust or authority be divided among multiple people to ensure checks and balances. This principle is focused on human-centric process control and accountability, not on the technical behavior or security state of an application when it encounters a system malfunction or unexpected operational error.
- ✓
Fail-secure
Why this is correct
Fail-secure, also known as fail-safe, is a critical design principle ensuring that if a system component or process fails, the system defaults to a state that denies access or prevents operations, thus maintaining security. For instance, a locked door remains locked if power fails, or an authentication system denies all access if its backend database becomes unavailable. This approach prioritizes security over availability during a failure event, directly addressing how an application should behave to protect data and resources.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official ISC2 exam blueprint
This CISSP practice question is part of Courseiva's free ISC2 certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CISSP exam.