This CKS practice question tests your understanding of system hardening. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 policy requires that all containers in the 'staging' namespace drop all Linux capabilities and only add the necessary ones. Which pod security context configuration achieves this?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
cap_drop: ["ALL"]
cap_add: ["NET_BIND_SERVICE"]
Option A is correct because the security policy requires dropping all Linux capabilities and only adding the necessary ones. The configuration `cap_drop: ["ALL"]` removes every capability from the container, and `cap_add: ["NET_BIND_SERVICE"]` explicitly adds back only the `CAP_NET_BIND_SERVICE` capability, which allows binding to privileged ports (below 1024). This follows the principle of least privilege by starting from a clean slate and granting only what is needed.
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.
✓
cap_drop: ["ALL"]
cap_add: ["NET_BIND_SERVICE"]
Why this is correct
Dropping all then adding only needed capabilities is the correct approach for least privilege.
Related concept
Read the scenario before looking for a memorised answer.
✗
cap_drop: ["NET_RAW"]
Why it's wrong here
This only drops NET_RAW, not all capabilities.
✗
cap_add: ["ALL"]
Why it's wrong here
This adds all capabilities, increasing the attack surface.
✗
cap_add: ["NET_BIND_SERVICE"]
Why it's wrong here
This adds capabilities but does not drop existing ones, so the container may still have default capabilities.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the misconception that simply adding a capability is sufficient, without realizing that the default capability set includes many capabilities (e.g., `CHOWN`, `DAC_OVERRIDE`, `FOWNER`, `FSETID`, `KILL`, `SETGID`, `SETUID`, `SETPCAP`, `NET_BIND_SERVICE`, `NET_RAW`, `SYS_CHROOT`, `MKNOD`, `AUDIT_WRITE`, `SETFCAP`) and that dropping all first is mandatory to enforce least privilege.
Detailed technical explanation
How to think about this question
In Kubernetes, Linux capabilities are managed via the `securityContext` at the pod or container level. The `cap_drop: ["ALL"]` directive is a common pattern to implement a default-deny approach, ensuring no inherited capabilities remain. The `cap_add` field then selectively grants specific capabilities; for example, `NET_BIND_SERVICE` corresponds to the `CAP_NET_BIND_SERVICE` capability (defined in Linux capabilities(7) man page), which is often needed for web servers like Nginx or Apache to bind to ports under 1024. This granular control is critical in multi-tenant clusters where container breakout risks must be minimized.
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.
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: cap_drop: ["ALL"]
cap_add: ["NET_BIND_SERVICE"] — Option A is correct because the security policy requires dropping all Linux capabilities and only adding the necessary ones. The configuration `cap_drop: ["ALL"]` removes every capability from the container, and `cap_add: ["NET_BIND_SERVICE"]` explicitly adds back only the `CAP_NET_BIND_SERVICE` capability, which allows binding to privileged ports (below 1024). This follows the principle of least privilege by starting from a clean slate and granting only what is needed.
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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