CISSP Software Development Security Practice Question
A security architect is designing a system that must continue to function even when a component fails. The architect implements multiple layers of security controls so that if one fails, others still provide protection. Which principle is being applied?
⚠ Common exam trap
Candidates often confuse 'defense in depth' with 'fail-secure' because both involve planning for failure, but fail-secure prioritizes security over availability (e.g., locking down on failure) whereas defense in depth prioritizes continued operation through redundancy of controls.
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
✓
Defense in depth
Defense in depth (B) is the correct principle because it involves implementing multiple layers of security controls (e.g., firewalls, intrusion detection systems, encryption, access controls) so that if one layer fails or is bypassed, other layers continue to provide protection, ensuring the system remains functional. This directly matches the scenario where the architect designs for continued operation despite component failure by layering controls.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Separation of duties
Why it's wrong here
This principle is an administrative control designed to mitigate the risk of fraud, error, and insider threat by distributing critical tasks among multiple individuals. It ensures that no single person possesses sufficient privileges to complete a sensitive operation entirely on their own, requiring collusion to bypass controls. While vital for governance, it does not directly address the architectural layering of diverse technical security mechanisms to protect against external attacks.
- ✓
Defense in depth
Why this is correct
This robust security strategy involves implementing multiple, independent, and overlapping security controls across various layers of an information system's architecture. By integrating administrative, technical, and physical safeguards, it ensures that if one control fails or is circumvented, other controls are still in place to detect, delay, or prevent an attack. This layered approach significantly increases the complexity and resources required for an adversary to achieve their objectives.
- ✗
Fail-secure
Why it's wrong here
The fail-secure principle dictates that when a system component experiences a failure, it should default to a state that denies access or operation, thereby preserving the confidentiality, integrity, and availability of data. This prevents unauthorized access or exploitation during system malfunctions. However, this principle specifically addresses system behavior upon failure rather than the proactive, multi-layered deployment of diverse security mechanisms intended to prevent initial compromise.
- ✗
Least privilege
Why it's wrong here
The principle of least privilege mandates that every user, program, or process should be granted only the minimum necessary permissions and access rights required to perform its specific authorized functions. This significantly reduces the potential impact of a security breach or error by limiting the scope of damage an attacker or compromised entity can inflict. While crucial for minimizing the attack surface, it focuses on access control granularity rather than the strategic deployment of multiple, distinct security layers throughout an entire system.
Go deeper
Related to this question
Learn chapter
Security Governance and Principles
Key term
Encryption
Encryption is the process of converting readable data into a secret code to prevent unauthorized access.
Key term
Security
Security in IT is the practice of protecting systems, networks, and data from unauthorized access, damage, or theft.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.