Question 1hardmulti select
Full question →- B
Use the latest base image from Docker Hub
Why wrong: This is important for image security, not runtime configuration.
Question 4 of 510
CAS-004 Secure container runtime Practice Question
This CAS-004 practice question tests your understanding of application environment, configuration and security. 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.
A security assessor is reviewing a containerized application. Which three of the following practices help secure the container runtime environment? (Select the three best options.)
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Run the container with a read-only root filesystem
Running a container with a read-only root filesystem (option A) prevents any writes to the container's filesystem layer, which blocks malware from dropping files, modifying binaries, or persisting changes. This is enforced by the container runtime (e.g., Docker, containerd) by mounting the root filesystem as read-only, typically using the `--read-only` flag. Even if an attacker gains code execution inside the container, they cannot alter system files or install tools, significantly reducing the blast radius of a compromise.
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.
- ✗
Use the latest base image from Docker Hub
Why it's wrong here
This is important for image security, not runtime configuration.
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.
✓Run the container with a read-only root filesystemCorrect answer▾
✗Use the latest base image from Docker HubWrong answer — click to see why▾
Why this is wrong here
This is important for image security, not runtime configuration.
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
CompTIA often tests the distinction between image security (e.g., using latest images) and runtime security (e.g., read-only filesystem, capability dropping, non-root user), and the trap here is that candidates may incorrectly select 'use the latest base image' because they conflate image freshness with runtime hardening.
Detailed technical explanation
How to think about this question
Under the hood, Linux capabilities are implemented via the `capability` kernel feature, which breaks down root privileges into distinct units (e.g., CAP_NET_BIND_SERVICE, CAP_SYS_ADMIN). Dropping all capabilities and adding only required ones (option C) follows the principle of least privilege, reducing the attack surface by preventing the container from performing privileged operations like loading kernel modules or changing system time. In a real-world scenario, a container running a web server might only need CAP_NET_BIND_SERVICE to bind to a low port, while all other capabilities are dropped, limiting damage if the web server process is compromised.
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.
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Application Environment, Configuration and Security — study guide chapter
Learn the concepts, then practise the questions
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FAQ
Questions learners often ask
What does this CAS-004 question test?
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: Run the container with a read-only root filesystem — Running a container with a read-only root filesystem (option A) prevents any writes to the container's filesystem layer, which blocks malware from dropping files, modifying binaries, or persisting changes. This is enforced by the container runtime (e.g., Docker, containerd) by mounting the root filesystem as read-only, typically using the `--read-only` flag. Even if an attacker gains code execution inside the container, they cannot alter system files or install tools, significantly reducing the blast radius of a compromise.
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.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 30, 2026
This CAS-004 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CAS-004 exam.
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