The correct answer is defense in depth and least privilege, as these are two foundational software development security principles. Defense in depth ensures that multiple layers of security controls are implemented so that if one layer fails, others still provide protection, preventing a single point of failure from compromising the entire system. Least privilege restricts user and process access to only the minimum resources necessary to perform their functions, reducing the attack surface and limiting potential damage from compromised accounts. On the CISSP exam, this question tests your ability to distinguish between core security principles and common pitfalls—for example, recognizing that “fail open” is insecure (the correct approach is fail closed) and that “security through obscurity” is not a reliable principle. A useful memory tip is to think of defense in depth as “layers of an onion” and least privilege as “need-to-know access”; together, they form the bedrock of secure software design.
CISSP Software Development Security Practice Question
This CISSP practice question tests your understanding of software development security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which TWO of the following are security principles that should be applied during software development? (Select TWO)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Least privilege
Options A and C are correct. Defense in depth (A) and least privilege (C) are fundamental security principles. Option B is wrong because single point of failure is a risk, not a principle. Option D is wrong because fail open is insecure; fail closed is preferred. Option E is wrong because security through obscurity is not a reliable principle.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Least privilege
Why this is correct
Least privilege ensures users and processes have only the minimum necessary permissions.
Related concept
Authentication checks who the user is.
✗
Security through obscurity
Why it's wrong here
Security through obscurity is not a reliable principle; it should not be solely relied upon.
✓
Defense in depth
Why this is correct
Defense in depth uses multiple layers of security to protect assets.
Related concept
Authentication checks who the user is.
✗
Single point of failure
Why it's wrong here
Single point of failure is a weakness, not a security principle.
✗
Fail open
Why it's wrong here
Fail open can allow unauthorized access; fail closed is the secure alternative.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
Authentication checks who the user is.
Authorization controls what the user is allowed to do after login.
Privilege levels affect access to EXEC and configuration commands.
AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
→Do not assume successful login means full administrative access.
→Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
→Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Real-world example
How this comes up in practice
A security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CISSP question in full detail.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CISSP questions on access control and AAA configuration.
Software Development Security — This question tests Software Development Security — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: Least privilege — Options A and C are correct. Defense in depth (A) and least privilege (C) are fundamental security principles. Option B is wrong because single point of failure is a risk, not a principle. Option D is wrong because fail open is insecure; fail closed is preferred. Option E is wrong because security through obscurity is not a reliable principle.
What should I do if I get this CISSP question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CISSP questions on access control and AAA configuration.
What is the key concept behind this question?
Authentication checks who the user is.
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