The answer is that the application would be denied write access to a file in /etc/config/. This is correct because AppArmor enforces mandatory access control by operating on a whitelist model: any action not explicitly permitted in the profile is denied by default. Since the exhibit’s profile lacks a rule allowing write operations to the /etc/config/ path, the kernel’s AppArmor LSM (Linux Security Module) blocks the write attempt, regardless of the application’s user identity or file permissions. On the CompTIA SecurityX CAS-004 exam, this tests your understanding of how AppArmor differs from discretionary access control (DAC) and SELinux—specifically, that AppArmor uses path-based restrictions rather than labels. A common trap is assuming standard Linux file permissions override the profile; they do not, as MAC supersedes DAC. For a memory tip, remember “AppArmor denies all unless allowed,” and think of the profile as a strict bouncer: if the path isn’t on the guest list, no entry.
CAS-004 Security Engineering Practice Question
This CAS-004 practice question tests your understanding of security engineering. 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Write to a file in /etc/config/
AppArmor profiles restrict applications by path and capability. The profile shown does not include any rule allowing write access to /etc/config/, so any write attempt to that directory or its files would be denied. This is because AppArmor enforces mandatory access control based on the profile's explicit allow rules.
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.
The capability dac_override is granted, so DAC override is allowed.
✗
Write to /var/log/app.log
Why it's wrong here
Write is explicitly allowed on /var/log/app.log.
✓
Write to a file in /etc/config/
Why this is correct
Only read is allowed on /etc/config/*; write is denied.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the misconception that AppArmor denies all actions not explicitly allowed, but candidates may overlook that network and capability rules are separate from file path rules, leading them to incorrectly assume a default allow for network or capability operations.
Detailed technical explanation
How to think about this question
AppArmor uses a 'deny by default, allow by explicit rule' model. The profile is parsed from top to bottom, and any path not covered by an 'r', 'w', 'rw', or 'l' rule is implicitly denied. In practice, administrators often forget to add rules for configuration directories like /etc/config/, leading to unexpected denials that can break application functionality.
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 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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Security Engineering — This question tests Security Engineering — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Write to a file in /etc/config/ — AppArmor profiles restrict applications by path and capability. The profile shown does not include any rule allowing write access to /etc/config/, so any write attempt to that directory or its files would be denied. This is because AppArmor enforces mandatory access control based on the profile's explicit allow rules.
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.
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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