The correct answer is to use signed images and verify signatures before deployment, along with implementing a read-only root filesystem. Signed images, validated through cryptographic verification, ensure that the container image has not been tampered with from its point of origin, directly enforcing integrity and supply chain security. A read-only root filesystem prevents any runtime modifications to the container’s base layer, which drastically reduces the attack surface by blocking malware persistence or configuration drift. On the CompTIA SecurityX CAS-004 exam, this question tests your understanding of container image security best practices within the domain of secure software development and deployment. A common trap is selecting options that improve performance or usability but weaken security, such as running containers as root or using mutable filesystems. Remember the mnemonic “Sign and Lock” — sign your images for integrity, and lock the filesystem to block runtime exploits.
CAS-004 Scripting, Containers and Automation Practice Question
This CAS-004 practice question tests your understanding of scripting, containers and automation. 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 is adopting container security best practices. Which TWO actions should be implemented to reduce the attack surface of container images? (Select TWO.)
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set the container filesystem as read-only where possible.
Using signed images (A) ensures integrity, and read-only root filesystem (C) prevents runtime modifications. Distractors B and D are insecure, and E is good but not as critical for attack surface reduction.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Set the container filesystem as read-only where possible.
Why this is correct
A read-only filesystem prevents attackers from writing malicious files.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✓
Use signed images and verify signatures before deployment.
Why this is correct
Image signing prevents tampering and ensures only trusted images are used.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
Disable vulnerability scanning to optimize build time.
Why it's wrong here
Vulnerability scanning is essential for security; disabling it increases risk.
✗
Store secrets in environment variables.
Why it's wrong here
Secrets in env vars can be leaked; use secret management tools instead.
✗
Run containers with the root user to simplify permissions.
Why it's wrong here
Running as root increases the risk of container escape and privilege escalation.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CAS-004 NAT questions on configuration and troubleshooting.
Scripting, Containers and Automation — This question tests Scripting, Containers and Automation — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Set the container filesystem as read-only where possible. — Using signed images (A) ensures integrity, and read-only root filesystem (C) prevents runtime modifications. Distractors B and D are insecure, and E is good but not as critical for attack surface reduction.
What should I do if I get this CAS-004 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CAS-004 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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Question Discussion
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