easyMultiple Choice
CAS-004 Practice Question: Implementing a risk management framework to…
A company is implementing a risk management framework to comply with PCI DSS. Which type of control is a firewall rule that blocks all inbound traffic except HTTP and HTTPS?
⚠ Common exam trap
Candidates often confuse 'preventive' with 'detective' because they think of firewall logs as detective, but the rule itself is a preventive control that stops traffic, while logging is a separate detective function.
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
✓
Preventive
A firewall rule that blocks all inbound traffic except HTTP (port 80) and HTTPS (port 443) is a preventive control because it actively enforces a security policy by denying unauthorized traffic before it can reach internal systems. This aligns with PCI DSS Requirement 1, which mandates a firewall configuration to restrict inbound traffic to only necessary services, thereby reducing the attack surface. Preventive controls are designed to stop security incidents from occurring, which is exactly what this rule accomplishes by filtering traffic at the network layer.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Corrective
Why it's wrong here
Corrective controls restore systems after an incident, such as backups or patching. A firewall rule denying all inbound traffic except HTTP and HTTPS stops the connection before it reaches the host, which is preventive; nothing is being corrected because the traffic never succeeds.
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Compensating
Why it's wrong here
Compensating controls substitute for a primary control that cannot be implemented, often for legacy constraints. This firewall rule is the primary preventive control itself, directly enforcing PCI DSS segmentation requirements, so no alternative or substitute control is being provided.
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Preventive
Why this is correct
A firewall rule permitting only HTTP and HTTPS denies all other inbound traffic before it reaches the target, which is the defining characteristic of a preventive control. This satisfies the stem's PCI DSS scenario by stopping unauthorised access attempts rather than detecting them afterwards.
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Detective
Why it's wrong here
A firewall rule permitting only HTTP and HTTPS prevents unauthorised traffic from reaching hosts, which is preventive, not detective. Detective controls identify and log events after they occur, such as IDS alerts or audit trails; blocking traffic outright is the preventive mechanism.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CAS-005 practice question is part of Courseiva's free CompTIA 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 CAS-005 exam.