CAS-004 Container root privilege mitigation Practice Question
This CAS-004 practice question tests your understanding of application environment, configuration and security. 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.
During a security review, a developer discovers that a containerized application runs with root privileges. Which of the following is the most secure approach to mitigate this risk while maintaining functionality?
Disable root login inside the container by modifying /etc/passwd
Why wrong: Disabling root login does not prevent the container process from running as root; the process still has root privileges.
C
Use a read-only root filesystem for the container
Why wrong: A read-only filesystem limits writes but does not reduce privileges; the container still runs as root.
D
Enable SELinux or AppArmor on the host
Why wrong: These are mandatory access control mechanisms that can confine a process, but they do not directly address the root privilege issue; combining with non-root user is better.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set the container to run as a non-root user and drop all unnecessary capabilities
Running a container as a non-root user with dropped capabilities is the most secure approach because it follows the principle of least privilege. By default, containers run as root, which grants unnecessary kernel capabilities that could be exploited for privilege escalation. Setting a non-root user and using `--cap-drop=ALL` with selective `--cap-add` ensures the application retains only required permissions, reducing the attack surface without breaking functionality.
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.
✗
Disable root login inside the container by modifying /etc/passwd
Why it's wrong here
Disabling root login does not prevent the container process from running as root; the process still has root privileges.
✗
Use a read-only root filesystem for the container
Why it's wrong here
A read-only filesystem limits writes but does not reduce privileges; the container still runs as root.
✗
Enable SELinux or AppArmor on the host
Why it's wrong here
These are mandatory access control mechanisms that can confine a process, but they do not directly address the root privilege issue; combining with non-root user is better.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The CAS-004 exam frequently reuses these exact scenarios with slightly different constraints.
✓Set the container to run as a non-root user and drop all unnecessary capabilitiesCorrect answer▾✗Disable root login inside the container by modifying /etc/passwdWrong answer — click to see why▾
Why this is wrong here
Disabling root login does not prevent the container process from running as root; the process still has root privileges.
✗Use a read-only root filesystem for the containerWrong answer — click to see why▾
Why this is wrong here
A read-only filesystem limits writes but does not reduce privileges; the container still runs as root.
✗Enable SELinux or AppArmor on the hostWrong answer — click to see why▾
Why this is wrong here
These are mandatory access control mechanisms that can confine a process, but they do not directly address the root privilege issue; combining with non-root user is better.
Analysis generated from the official CAS-004blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that disabling root login or using filesystem restrictions (read-only) is sufficient, when the real risk is the container process running as UID 0 with full capabilities, which requires explicit user context and capability dropping to mitigate.
Detailed technical explanation
How to think about this question
Under the hood, Linux capabilities are a granular set of privileges (e.g., CAP_NET_BIND_SERVICE, CAP_SYS_ADMIN) that can be assigned to processes regardless of UID. Dropping all capabilities with `--cap-drop=ALL` and adding only those required (e.g., `--cap-add=NET_BIND_SERVICE`) ensures the container process, even if compromised, cannot perform privileged operations like raw socket access or kernel module loading. In real-world scenarios, this is critical for multi-tenant container platforms like Kubernetes, where a root container could escape to the host via CVE-2019-5736 or similar vulnerabilities.
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 junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
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.
Application Environment, Configuration and Security — This question tests Application Environment, Configuration and Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Set the container to run as a non-root user and drop all unnecessary capabilities — Running a container as a non-root user with dropped capabilities is the most secure approach because it follows the principle of least privilege. By default, containers run as root, which grants unnecessary kernel capabilities that could be exploited for privilege escalation. Setting a non-root user and using `--cap-drop=ALL` with selective `--cap-add` ensures the application retains only required permissions, reducing the attack surface without breaking functionality.
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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