The answer is deploying a firewall between the CDE and corporate network, allowing only necessary traffic. This is correct because a properly configured firewall with a default-deny policy creates a strict network segmentation boundary, isolating the cardholder data environment from the rest of the network. By restricting traffic to only what is required for business functionality, you effectively reduce PCI DSS scope—only systems inside the segmented CDE must comply with full PCI requirements, while the corporate network falls out of scope. On the CompTIA SecurityX CAS-004 exam, this tests your understanding of PCI DSS Requirement 1 and the practical application of network segmentation for scope reduction. A common trap is assuming that simply placing systems on separate VLANs or using ACLs alone is sufficient; the exam expects a stateful firewall enforcing explicit allow rules. Remember the mnemonic “Firewall First” to recall that a dedicated firewall boundary, not just logical separation, is the key to shrinking PCI scope.
CAS-004 Governance, Risk and Compliance Practice Question
This CAS-004 practice question tests your understanding of governance, risk and compliance. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
You are the security architect for a mid-sized e-commerce company that processes credit card payments. The company must comply with PCI DSS. Currently, the cardholder data environment (CDE) includes a web server, an application server, and a database server, all on the same flat network segment. The QSA has identified that the CDE is not properly segmented, and network access controls are insufficient. The company wants to minimize the scope of PCI compliance by reducing the number of systems that handle cardholder data. You propose implementing network segmentation to isolate the CDE. Which of the following is the most effective approach to reduce PCI scope while maintaining business functionality?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Deploy a firewall between the CDE and corporate network, allowing only necessary traffic
Option D is correct because deploying a firewall between the CDE and the corporate network, and restricting traffic to only what is necessary, creates a proper network segmentation boundary. This isolation reduces the PCI DSS scope by ensuring that only systems within the CDE are subject to the full set of PCI requirements, while the corporate network remains out of scope. The firewall enforces a default-deny policy, which aligns with PCI DSS Requirement 1 for network segmentation and access control.
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.
✗
Encrypt all cardholder data at rest and in transit
Why it's wrong here
Encryption does not remove systems from scope
✗
Replace the database with a tokenization service and remove the database from the CDE
Why it's wrong here
Tokenization can reduce scope but the question is about segmentation
✗
Move all servers to a DMZ and implement host-based firewalls
Why it's wrong here
Still in scope if they handle cardholder data
✓
Deploy a firewall between the CDE and corporate network, allowing only necessary traffic
Why this is correct
Segmenting the CDE reduces scope
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse data-centric controls (like encryption or tokenization) with network-centric controls (like segmentation), leading them to choose options that protect data but do not reduce the number of systems in the CDE.
Detailed technical explanation
How to think about this question
Network segmentation for PCI DSS relies on a firewall or equivalent device that enforces a clear boundary between the CDE and untrusted networks, using a default-deny rule set that only permits explicitly required traffic (e.g., HTTPS from the web server to the application server). Under the hood, this segmentation is often validated by the QSA through network diagrams and firewall rule reviews, and it must be maintained with change control processes. A real-world scenario where this matters is when a company uses a flat network; without segmentation, every system in the same broadcast domain could be considered in scope, dramatically increasing compliance costs.
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 security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Governance, Risk and Compliance — This question tests Governance, Risk and Compliance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Deploy a firewall between the CDE and corporate network, allowing only necessary traffic — Option D is correct because deploying a firewall between the CDE and the corporate network, and restricting traffic to only what is necessary, creates a proper network segmentation boundary. This isolation reduces the PCI DSS scope by ensuring that only systems within the CDE are subject to the full set of PCI requirements, while the corporate network remains out of scope. The firewall enforces a default-deny policy, which aligns with PCI DSS Requirement 1 for network segmentation and access control.
What should I do if I get this CAS-004 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: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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