The correct answer is to implement Docker Content Trust with a Notary server to require signatures on all images. This solution ensures container image integrity by enabling cryptographic signing and verification, so any tampered image is rejected before deployment. Docker Content Trust leverages a Notary server to manage the signing keys and metadata, creating a chain of trust that validates the image publisher and content. On the CompTIA SecurityX CAS-004 exam, this scenario tests your understanding of supply chain security and integrity controls, often appearing as a distractor against SSH key authentication or simple encryption—neither of which provides non-repudiation or tamper evidence. A common trap is confusing image signing with registry access control; remember that signing proves *who* signed it and that the content hasn’t changed, while a private registry alone only restricts who can push. Memory tip: “Sign before you ship, Notary keeps the grip.”
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 security analyst discovers that container images in the company's private registry lack signatures. The development team uses a script to build and push images. The analyst wants to ensure image integrity and prevent tampering. Which solution should the analyst recommend?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Implement Docker Content Trust with a Notary server to require signatures on all images.
Docker Content Trust (Notary) provides image signing and verification. Option A is correct. SSH keys (B) are not designed for image signing. Encryption (C) does not provide integrity. Private registry only (D) does not prevent tampering after push.
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.
✓
Implement Docker Content Trust with a Notary server to require signatures on all images.
Why this is correct
Docker Content Trust uses signing keys and a Notary server to verify image integrity at pull time.
Related concept
Static NAT maps one inside address to one outside address.
✗
Restrict registry access to only the build servers.
Why it's wrong here
Access control reduces risk but does not provide integrity verification; images could still be tampered with on the registry.
✗
Use SSH keys to sign the image tarball before pushing.
Why it's wrong here
SSH keys are not integrated with Docker's trust model and would require custom verification.
✗
Encrypt the image filesystem layer using AES-256.
Why it's wrong here
Encryption protects confidentiality, not integrity; it does not prevent tampering.
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: Implement Docker Content Trust with a Notary server to require signatures on all images. — Docker Content Trust (Notary) provides image signing and verification. Option A is correct. SSH keys (B) are not designed for image signing. Encryption (C) does not provide integrity. Private registry only (D) does not prevent tampering after push.
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.
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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