Quick Answer
The answer is preventive, because a firewall rule that blocks all inbound traffic except HTTP and HTTPS is designed to stop unauthorized access before it can occur, which is the defining characteristic of a preventive control in PCI DSS. This type of control actively enforces security policies by restricting traffic at the network perimeter, directly reducing the attack surface. On the CompTIA SecurityX CAS-004 exam, this concept tests your ability to classify controls within a risk management framework, often appearing in scenario-based questions where you must distinguish preventive controls from detective, corrective, or compensating alternatives. A common trap is confusing a firewall rule with a detective control, but remember that prevention happens before the event, while detection happens after. To lock it in, use the mnemonic “Preventive Blocks, Detective Watches”—if the control stops the action, it’s preventive.
This CAS-004 practice question tests your understanding of governance, risk and compliance. 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 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?
Corrective
Why wrong: Corrective controls remediate issues after detection, not prevent.
Compensating
Why wrong: Compensating controls are alternative controls when primary controls are not feasible.
Preventive
Preventive controls block or avoid security incidents.
Detective
Why wrong: Detective controls identify incidents after they occur, not prevent them.
Answer choices
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 traffic is a preventive control because it prevents unauthorized access. Detective controls identify incidents after they occur, corrective controls fix issues, and compensating controls provide alternative security.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Corrective
Why it's wrong here
Corrective controls remediate issues after detection, not prevent.
Compensating
Why it's wrong here
Compensating controls are alternative controls when primary controls are not feasible.
Preventive
Why this is correct
Preventive controls block or avoid security incidents.
Related concept
Static NAT maps one inside address to one outside address.
Detective
Why it's wrong here
Detective controls identify incidents after they occur, not prevent them.
Common exam traps
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CAS-004 NAT questions on configuration and troubleshooting.
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FAQ
Governance, Risk and Compliance — This question tests Governance, Risk and Compliance — Static NAT maps one inside address to one outside address..
The correct answer is: Preventive — A firewall rule that blocks traffic is a preventive control because it prevents unauthorized access. Detective controls identify incidents after they occur, corrective controls fix issues, and compensating controls provide alternative security.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CAS-004 NAT questions on configuration and troubleshooting.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 24, 2026
This CAS-004 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-004 exam.
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