The correct choice is to rebuild the container images using minimal base images and remove unnecessary packages. This directly reduces the attack surface by stripping away extraneous tools, libraries, and binaries that attackers could exploit, aligning with the principle of least functionality. On the CompTIA SecurityX CAS-004 exam, this scenario tests your understanding of container hardening within Kubernetes security, where the common trap is to jump to running containers as non-root—a valid step, but one that doesn’t address the software footprint. Remember, minimal base images like Alpine or distroless are the first line of defense against package bloat; think of them as a “clean slate” that eliminates the need to patch or remove what isn’t there. A helpful memory tip: “Trim the fat before you lock the door”—reduce packages first, then enforce non-root and read-only filesystems.
CAS-004 Practice Question: Application Environment, Configuration and Security
This CAS-004 practice question tests your understanding of application environment, configuration and security. 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.
A company runs a containerized application in a Kubernetes cluster. After a penetration test, the security team found that several containers are running with root privileges and have unnecessary packages installed. To reduce the attack surface, the team wants to enforce least privilege and minimize the software footprint. Which action should be taken first to address these findings?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Clue: "least"
Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
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
✓
Rebuild the container images using minimal base images and remove unnecessary packages
Using minimal base images (e.g., Alpine or distroless) reduces the attack surface by removing unnecessary tools and libraries. Option B is incorrect because running containers as non-root is important but does not address unnecessary packages. Option C is incorrect because read-only filesystems improve security but do not reduce the number of packages. Option D is incorrect because network policies control traffic but not container privileges or packages.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Apply SELinux labels to restrict container capabilities
Why it's wrong here
SELinux adds mandatory access control but does not remove packages.
✓
Rebuild the container images using minimal base images and remove unnecessary packages
Why this is correct
Minimal images reduce attack surface by eliminating unnecessary components.
Clue confirmation
The clue words "first", "least", "minimum / minimize" in the question point toward this answer.
Related concept
Authentication checks who the user is.
✗
Configure the containers to run as non-root user and use read-only filesystems
Why it's wrong here
This addresses privilege escalation but not the unnecessary packages.
✗
Implement network policies to limit lateral movement between pods
Why it's wrong here
Network policies are important but do not reduce the software footprint of containers.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
Authentication checks who the user is.
Authorization controls what the user is allowed to do after login.
Privilege levels affect access to EXEC and configuration commands.
AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
→Do not assume successful login means full administrative access.
→Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
→Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
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.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CAS-004 questions on access control and AAA configuration.
Application Environment, Configuration and Security — This question tests Application Environment, Configuration and Security — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: Rebuild the container images using minimal base images and remove unnecessary packages — Using minimal base images (e.g., Alpine or distroless) reduces the attack surface by removing unnecessary tools and libraries. Option B is incorrect because running containers as non-root is important but does not address unnecessary packages. Option C is incorrect because read-only filesystems improve security but do not reduce the number of packages. Option D is incorrect because network policies control traffic but not container privileges or packages.
What should I do if I get this CAS-004 question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CAS-004 questions on access control and AAA configuration.
Are there clue words in this question I should notice?
Yes — watch for: "first", "least", "minimum / minimize". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Authentication checks who the user is.
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