This CKS practice question tests your understanding of system hardening. 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.
What is the default seccomp profile applied when a pod's security context has 'seccompProfile.type: RuntimeDefault'?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The container runtime's default seccomp profile, which blocks around 40 syscalls
Option D is correct because when `seccompProfile.type: RuntimeDefault` is set in a pod's security context, the container runtime (e.g., containerd or CRI-O) applies its own default seccomp profile. This runtime default profile is a curated allowlist that blocks approximately 40 syscalls known to be dangerous or unnecessary for containers, providing a balance between security and compatibility. It is not the Docker default (which blocks ~300 syscalls) but a more permissive profile tailored to the runtime's container model.
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.
✗
The profile defined in /var/lib/kubelet/seccomp/default.json
Why it's wrong here
RuntimeDefault does not look for a local file; it uses the runtime's built-in profile.
✗
Unconfined (no seccomp)
Why it's wrong here
Unconfined disables seccomp entirely. RuntimeDefault uses a default profile.
✗
The Docker default profile, which blocks around 300 syscalls
Why it's wrong here
Docker's default profile is not used by Kubernetes; the runtime's default is used.
✓
The container runtime's default seccomp profile, which blocks around 40 syscalls
Why this is correct
RuntimeDefault instructs the container runtime (e.g., containerd) to apply its own default seccomp policy.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the misconception that `RuntimeDefault` refers to Docker's legacy default profile (which blocks ~300 syscalls), when in fact it refers to the container runtime's own default (which blocks ~40 syscalls), and candidates may confuse it with `Unconfined` or a custom localhost path.
Detailed technical explanation
How to think about this question
Under the hood, the container runtime (e.g., containerd) ships a default seccomp profile that is compiled into the runtime binary or loaded from a default path like `/etc/containerd/seccomp.json`. This profile uses a whitelist approach, allowing most syscalls but blocking high-risk ones such as `mount`, `ptrace`, and `perf_event_open`. In a real-world scenario, if a pod requires additional syscalls (e.g., for performance monitoring), you must override `RuntimeDefault` with a custom `Localhost` profile, as the runtime default is intentionally restrictive to reduce kernel attack surface.
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 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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKS question in full detail.
System Hardening — This question tests System Hardening — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The container runtime's default seccomp profile, which blocks around 40 syscalls — Option D is correct because when `seccompProfile.type: RuntimeDefault` is set in a pod's security context, the container runtime (e.g., containerd or CRI-O) applies its own default seccomp profile. This runtime default profile is a curated allowlist that blocks approximately 40 syscalls known to be dangerous or unnecessary for containers, providing a balance between security and compatibility. It is not the Docker default (which blocks ~300 syscalls) but a more permissive profile tailored to the runtime's container model.
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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