This SSCP practice question tests your understanding of security operations and administration. 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.
A security engineer is configuring a firewall to block all inbound traffic except for specific services. Which of the following design principles is being applied?
Separation of duties
Why wrong: Separation of duties divides responsibilities among different individuals.
Default deny
Why wrong: Default deny is a configuration of the firewall, not the principle behind it.
Defense in depth
Why wrong: Defense in depth uses multiple layers of security.
Least privilege
Least privilege ensures entities have only the access needed to perform their functions.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Least privilege
The correct answer is D, Least Privilege, because the security engineer is configuring the firewall to block all inbound traffic except for specific services. This aligns with the principle of least privilege, which dictates that only the minimum necessary access should be granted—in this case, only allowing specific services through while denying everything else by default. The firewall rule set explicitly permits only required ports (e.g., TCP/443 for HTTPS) and implicitly denies all other traffic, ensuring that no unnecessary access is permitted.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
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
Separation of duties divides responsibilities among different individuals.
Default deny
Why it's wrong here
Default deny is a configuration of the firewall, not the principle behind it.
Defense in depth
Why it's wrong here
Defense in depth uses multiple layers of security.
Least privilege
Why this is correct
Least privilege ensures entities have only the access needed to perform their functions.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates confuse the 'default deny' mechanism (a firewall policy stance) with the 'least privilege' design principle, but the question asks for the overarching principle, not the specific implementation method.
Detailed technical explanation
Under the hood, a firewall implementing least privilege uses an implicit deny rule at the end of its Access Control List (ACL), meaning any packet not matching an explicit permit rule is dropped. In real-world scenarios, this prevents lateral movement in a network; for example, a web server might only have TCP/443 and TCP/22 (SSH) permitted, blocking all other ports to reduce the attack surface. The principle is codified in RFC 2827 (BCP 38) for ingress filtering and is a core tenet of Zero Trust architectures.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
What to study next
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FAQ
Security Operations and Administration — This question tests Security Operations and Administration — Read the scenario before looking for a memorised answer..
The correct answer is: Least privilege — The correct answer is D, Least Privilege, because the security engineer is configuring the firewall to block all inbound traffic except for specific services. This aligns with the principle of least privilege, which dictates that only the minimum necessary access should be granted—in this case, only allowing specific services through while denying everything else by default. The firewall rule set explicitly permits only required ports (e.g., TCP/443 for HTTPS) and implicitly denies all other traffic, ensuring that no unnecessary access is permitted.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
This SSCP 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 SSCP exam.
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