The most effective compensating control for unencrypted data at rest in a legacy database is isolating the database server on a separate network segment with strict firewall rules. This works because network segmentation, using VLANs and access control lists, restricts all traffic to only the specific IP and port of the legacy application, thereby preventing unauthorized network-level access to the unencrypted data. On the CISA exam, this scenario tests your understanding of defense-in-depth and compensating controls when encryption is technically infeasible—a common trap is choosing data masking or tokenization, but those require application changes, which the prompt explicitly forbids. The key insight is that you are reducing the attack surface by controlling who can reach the data, not by altering the data itself. Memory tip: when encryption is blocked, think “block the path”—segment and isolate.
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.
During a security audit, it is discovered that a database containing customer credit card numbers is not encrypted at rest. The database is used by a legacy application that cannot be modified. Which compensating control most effectively reduces the risk?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Isolating the database server on a separate network segment with strict firewall rules
Isolating the database server on a separate network segment with strict firewall rules (e.g., using VLANs and ACLs to restrict traffic to only the legacy application’s IP and port) prevents unauthorized network-level access to the unencrypted data. This compensating control reduces the attack surface by ensuring that even if the database lacks encryption at rest, an attacker cannot reach it without first compromising the network segmentation, which is a critical defense-in-depth layer.
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.
✓
Isolating the database server on a separate network segment with strict firewall rules
Why this is correct
Segmentation reduces the attack surface and limits access.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enabling detailed audit logging for all database access
Why it's wrong here
Logging is detective, not preventive.
✗
Requiring all users to sign a nondisclosure agreement (NDA)
Why it's wrong here
NDA is a legal control, not technical.
✗
Implementing dynamic data masking at the application level
Why it's wrong here
Masking hides data from users but data remains unencrypted in storage.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose audit logging or masking because they seem technical, but they fail to recognize that only network segmentation actively prevents direct access to the unencrypted data at rest, while the others are either detective or require application changes that are impossible in this scenario.
Detailed technical explanation
How to think about this question
Network segmentation for a legacy database often involves placing the server in a dedicated DMZ or isolated VLAN with a stateful firewall that permits only specific protocols (e.g., TCP/1433 for SQL Server or TCP/3306 for MySQL) from a single source IP of the legacy application. This approach leverages the principle of least privilege at the network layer, and if the database uses unencrypted TDS or MySQL protocol, segmentation prevents lateral movement from compromised hosts. In real-world scenarios, this is commonly used when patching or encrypting legacy systems is infeasible, such as in mainframe or COBOL-based applications that lack encryption support.
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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
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.
Protection of Information Assets — This question tests Protection of Information Assets — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Isolating the database server on a separate network segment with strict firewall rules — Isolating the database server on a separate network segment with strict firewall rules (e.g., using VLANs and ACLs to restrict traffic to only the legacy application’s IP and port) prevents unauthorized network-level access to the unencrypted data. This compensating control reduces the attack surface by ensuring that even if the database lacks encryption at rest, an attacker cannot reach it without first compromising the network segmentation, which is a critical defense-in-depth layer.
What should I do if I get this CISA question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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