ISC2 CC Access Controls Concepts Practice Question
A company configures its firewall to block all inbound traffic except for specific necessary services. This approach aligns with which access control principle?
⚠ Common exam trap
CC often tests the confusion between least privilege (minimum necessary access) and defense in depth (layered controls) — candidates pick 'defense in depth' whenever a firewall is mentioned, even when the scenario is about minimizing allowed access.
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
✓
Least privilege
Blocking all inbound traffic except explicitly required services is the definition of least privilege applied to network access control — granting only the minimum access necessary for business function. The firewall default-deny with specific allow rules embodies this principle by minimizing the attack surface.
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
Separation of duties splits critical tasks among multiple people to prevent fraud, which a firewall rule set does not achieve. It is tempting because both are access control principles, and separation of duties is correct when a scenario requires two individuals to complete a sensitive transaction, such as one approving payments another creates.
- ✗
Defense in depth
Why it's wrong here
Defense in depth layers multiple independent controls; a single firewall rule blocking inbound traffic is one control at one boundary. It is tempting because firewalls commonly form part of layered architectures, and defense in depth is correct when a scenario describes several overlapping safeguards, such as firewalls, endpoint protection and physical locks together.
- ✗
Need-to-know
Why it's wrong here
Need-to-know restricts data access to individuals whose duties require specific information, not which network services are reachable. It is tempting because both limit access, and need-to-know is correct when a scenario restricts a person's access to particular data, such as denying payroll records to staff outside HR.
- ✓
Least privilege
Why this is correct
Default-deny firewall rules permit only explicitly required services, embodying least privilege by granting the minimum access necessary. This satisfies the stem's constraint of blocking all inbound traffic except specific necessary services, rather than relying on implicit trust.
Go deeper
Related to this question
Learn chapter
Access Control Fundamentals
Key term
Firewall
A firewall is a network security system that monitors and controls incoming and outgoing traffic based on predetermined security rules to protect trusted internal networks from untrusted external networks.
Key term
Access control
Access control is the security practice of determining who or what is allowed to view, use, or enter a resource, and under what conditions.
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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 CC 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 CC exam.