The answer is to remove the fallback mechanism and ensure the tokenization system has appropriate redundancy. This is correct because the fallback directly exposes full cardholder data when the tokenization system fails, which violates PCI DSS Requirement 3 to protect stored card data at rest; no amount of encryption or key separation can compensate for a process that deliberately writes raw primary account numbers to a database. On the CISA exam, this scenario tests your ability to prioritize remediation based on risk severity—the fallback creates an immediate, uncontrolled data exposure, whereas key separation (a common distractor) is a secondary control issue. A frequent trap is choosing redundancy for the tokenization system, but that addresses performance, not the direct violation of storing card data without authorization. Memory tip: “Fallback fails first—fix the leak before you fix the pipe.”
CISA Protection of Information Assets Practice Question
This CISA practice question tests your understanding of protection of information assets. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
An e-commerce company stores customer payment card data in a tokenized database. The tokenization system replaces credit card numbers with tokens, and the actual card numbers are stored in a separate, highly restricted vault. The company is audited for Payment Card Industry Data Security Standard (PCI DSS) compliance. During the audit, it is discovered that the tokenization system sometimes fails due to high load, causing the application to fall back to storing actual card numbers temporarily. This fallback mechanism was not documented or approved. The company also uses the same encryption key for the vault as for other non-sensitive data. The auditor identifies several non-compliances. Which of the following should the company prioritize to remediate?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Remove the fallback mechanism and ensure the tokenization system has appropriate redundancy
Option D is correct because the fallback mechanism directly exposes cardholder data, violating PCI DSS requirement to protect stored card data. Correcting this eliminates the risk. Option A is important but not as immediate. Option B (redundancy) is a performance issue. Option C (key separation) is also critical, but the fallback is a direct data exposure.
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
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Replace the tokenization system with end-to-end encryption
Why it's wrong here
End-to-end encryption is a different approach, but the immediate issue is the fallback.
✓
Remove the fallback mechanism and ensure the tokenization system has appropriate redundancy
Why this is correct
Eliminating the fallback prevents storage of raw card numbers.
Related concept
Static NAT maps one inside address to one outside address.
✗
Use a separate encryption key for the vault
Why it's wrong here
Key separation is important but secondary to the fallback issue.
✗
Increase the capacity of the tokenization server to handle peak loads
Why it's wrong here
This addresses performance, not the fallback flaw.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
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
How to think about this question
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.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
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
How this comes up in practice
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
Got this wrong? Here's your next step.
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 CISA NAT questions on configuration and troubleshooting.
Protection of Information Assets — This question tests Protection of Information Assets — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Remove the fallback mechanism and ensure the tokenization system has appropriate redundancy — Option D is correct because the fallback mechanism directly exposes cardholder data, violating PCI DSS requirement to protect stored card data. Correcting this eliminates the risk. Option A is important but not as immediate. Option B (redundancy) is a performance issue. Option C (key separation) is also critical, but the fallback is a direct data exposure.
What should I do if I get this CISA question wrong?
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 CISA NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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