This CKS practice question tests your understanding of supply chain 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.
You are auditing a cluster's supply chain security. You find that many pods are running images from public registries without any pinning or verification. Which TWO actions would most effectively reduce the risk of pulling malicious images?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure all deployments to use image digests instead of tags.
Option A is correct because using image digests (e.g., `nginx@sha256:abc123...`) pins the image to an immutable content hash, ensuring that the exact same image is pulled every time, even if the tag is updated to a malicious version. This prevents tag-mutation attacks where an attacker replaces a benign image tag with a compromised one. Digests are verified by the container runtime (containerd) against the registry's manifest, providing cryptographic assurance of image integrity.
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.
✓
Configure all deployments to use image digests instead of tags.
Why this is correct
Prevents tag mutation and ensures image integrity.
Related concept
Read the scenario before looking for a memorised answer.
✓
Set up a private registry proxy that mirrors approved public images and disable direct access to public registries via containerd configuration.
Why this is correct
Proxies allow control and scanning of images.
Related concept
Read the scenario before looking for a memorised answer.
✗
Implement RBAC to restrict which users can create pods.
Why it's wrong here
Does not prevent pulling malicious images by authorized users.
✗
Enforce PodSecurityStandard baseline or restricted to block privileged containers.
Why it's wrong here
Does not control image source.
✗
Apply a network policy that blocks egress traffic to public registries.
Why it's wrong here
Network policies do not affect image pulling; kubelet pulls images before starting pods.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the distinction between runtime security controls (PodSecurityStandards, network policies) and supply chain controls (image pinning, registry proxies), and candidates mistakenly think blocking egress or restricting pod creation mitigates the risk of pulling malicious images, when those controls do not affect the image pull process itself.
Detailed technical explanation
How to think about this question
Image digests are derived from the manifest's SHA-256 hash, which includes layer digests and configuration; changing even a single byte in the image changes the digest. When using containerd, the `image` field in the pod spec can reference a digest directly, and the runtime will verify the digest against the registry's response. A real-world scenario is the `kube-controller-manager` image being pulled with a mutable tag like `v1.24.0`; an attacker could push a malicious image with the same tag to a public registry, but using the digest `sha256:...` prevents this entirely.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKS question in full detail.
Supply Chain Security — This question tests Supply Chain Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure all deployments to use image digests instead of tags. — Option A is correct because using image digests (e.g., `nginx@sha256:abc123...`) pins the image to an immutable content hash, ensuring that the exact same image is pulled every time, even if the tag is updated to a malicious version. This prevents tag-mutation attacks where an attacker replaces a benign image tag with a compromised one. Digests are verified by the container runtime (containerd) against the registry's manifest, providing cryptographic assurance of image integrity.
What should I do if I get this CKS 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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