The answer is defense in depth, the correct security principle for this layered strategy. This approach relies on deploying multiple independent security controls—such as a firewall, intrusion detection system, antivirus, and multi-factor authentication—so that if one layer fails or is bypassed, another layer can still prevent, detect, or mitigate an attack. The architect’s explanation explicitly illustrates redundancy and diversity of controls, which is the technical core of defense in depth layered security. On the SC-900 exam, this concept tests your understanding of how overlapping controls create resilience, often appearing in scenario-based questions where a single control is compromised. A common trap is confusing defense in depth with a single strong control; remember that the key is multiple independent layers, not just one robust solution. A useful memory tip is “layers like an onion”—peel one back, and another still protects.
SC-900 Practice Question: Describe the concepts of security, compliance, and identity
This SC-900 practice question tests your understanding of describe the concepts of security, compliance, and identity. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A security architect is designing a defense strategy for a company's IT infrastructure. The strategy includes deploying a network firewall, using an intrusion detection system, installing antivirus software on all endpoints, and requiring multi-factor authentication for all user accounts. The architect explains that if the firewall fails, the IDS can detect an intrusion, and if the IDS misses something, the antivirus might catch it, and MFA can protect even if credentials are compromised. Which security principle best describes this layered approach?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Defense in depth uses multiple overlapping security controls so that the failure of one layer does not leave the organization unprotected.
B
Least privilege
Why wrong: Least privilege is about limiting user permissions to the minimum necessary, not about multiple layers of controls.
C
Zero Trust
Why wrong: Zero Trust is a security model that eliminates trust based on network location and requires continuous verification, but it is not specifically the layered control concept described.
D
Shared responsibility
Why wrong: Shared responsibility is a cloud computing model that defines which security tasks are handled by the provider versus the customer, not a defense-in-depth strategy.
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 is the correct principle because it describes a layered security strategy where multiple independent controls (firewall, IDS, antivirus, MFA) are deployed so that if one layer fails, another layer can still prevent or detect an attack. This approach explicitly relies on redundancy and diversity of controls to provide resilience against failures or bypasses, as illustrated by the architect's explanation of how each subsequent layer compensates for potential gaps in the previous one.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Defense in depth
Why this is correct
Defense in depth uses multiple overlapping security controls so that the failure of one layer does not leave the organization unprotected.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Least privilege
Why it's wrong here
Least privilege is about limiting user permissions to the minimum necessary, not about multiple layers of controls.
✗
Zero Trust
Why it's wrong here
Zero Trust is a security model that eliminates trust based on network location and requires continuous verification, but it is not specifically the layered control concept described.
✗
Shared responsibility
Why it's wrong here
Shared responsibility is a cloud computing model that defines which security tasks are handled by the provider versus the customer, not a defense-in-depth strategy.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse 'Defense in depth' with 'Zero Trust' because both involve multiple controls, but Zero Trust is specifically about continuous verification and micro-segmentation, not the layered redundancy described in the scenario.
Detailed technical explanation
How to think about this question
Defense in depth relies on the principle of 'security in layers' where each layer addresses different attack vectors or failure modes. For example, a network firewall (e.g., stateful inspection at OSI Layer 3/4) can be bypassed by application-layer attacks, which an IDS (e.g., Snort analyzing packet payloads for signatures) might detect, while antivirus (e.g., signature-based and heuristic scanning on endpoints) catches malware that evades network controls. MFA (e.g., TOTP or FIDO2) adds an authentication layer independent of network and endpoint security, protecting against credential theft even if other layers are compromised.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this SC-900 question in full detail.
Describe the concepts of security, compliance, and identity — This question tests Describe the concepts of security, compliance, and identity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Defense in depth — Defense in depth is the correct principle because it describes a layered security strategy where multiple independent controls (firewall, IDS, antivirus, MFA) are deployed so that if one layer fails, another layer can still prevent or detect an attack. This approach explicitly relies on redundancy and diversity of controls to provide resilience against failures or bypasses, as illustrated by the architect's explanation of how each subsequent layer compensates for potential gaps in the previous one.
What should I do if I get this SC-900 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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