- A
Set --read-only-port=10255
Why wrong: Setting --read-only-port exposes an unauthenticated read-only endpoint; this does not harden against unauthorized access and actually increases the attack surface.
- B
Enable --authentication-token-webhook
Why wrong: Enabling --authentication-token-webhook allows the kubelet to validate bearer tokens via the API server's webhook token review. However, this alone does not harden the kubelet because anonymous requests are still accepted by default unless --anonymous-auth is set to false and client certificate authentication is configured. Therefore, it is not an effective standalone hardening measure.
- C
Enable the NodeRestriction admission controller
The NodeRestriction admission controller limits the Node and Pod objects a kubelet can modify, preventing a compromised node from escalating privileges or tampering with other workloads. This is a key Kubernetes-native control to harden the kubelet's authorization scope and is therefore effective.
- D
Configure --client-ca-file and --tls-cert-file to require client certificates
Configuring --client-ca-file and --tls-cert-file forces the kubelet to require and validate client certificates for all incoming requests, ensuring only authenticated clients can access the kubelet API. This is a strong authentication mechanism that effectively hardens against unauthorized access.
- E
Set --anonymous-auth=true
Why wrong: This would allow unauthenticated access, weakening security.
Hardening the Kubelet Against Unauthorized Access
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.
Which TWO of the following are effective methods to harden the kubelet against unauthorized access?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Enable the NodeRestriction admission controller
Option C is correct because the NodeRestriction admission controller limits the Node and Pod objects a kubelet can modify, preventing a compromised node from escalating privileges or tampering with other workloads. This is a key Kubernetes-native control to harden the kubelet's authorization scope.
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.
- ✗
Set --read-only-port=10255
Why it's wrong here
Setting --read-only-port exposes an unauthenticated read-only endpoint; this does not harden against unauthorized access and actually increases the attack surface.
- ✗
Enable --authentication-token-webhook
Why it's wrong here
Enabling --authentication-token-webhook allows the kubelet to validate bearer tokens via the API server's webhook token review. However, this alone does not harden the kubelet because anonymous requests are still accepted by default unless --anonymous-auth is set to false and client certificate authentication is configured. Therefore, it is not an effective standalone hardening measure.
- ✓
Enable the NodeRestriction admission controller
Why this is correct
The NodeRestriction admission controller limits the Node and Pod objects a kubelet can modify, preventing a compromised node from escalating privileges or tampering with other workloads. This is a key Kubernetes-native control to harden the kubelet's authorization scope and is therefore effective.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Configure --client-ca-file and --tls-cert-file to require client certificates
Why this is correct
Configuring --client-ca-file and --tls-cert-file forces the kubelet to require and validate client certificates for all incoming requests, ensuring only authenticated clients can access the kubelet API. This is a strong authentication mechanism that effectively hardens against unauthorized access.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Set --anonymous-auth=true
Why it's wrong here
This would allow unauthenticated access, weakening security.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the distinction between authentication (verifying identity) and authorization (limiting actions); candidates may confuse enabling authentication (Option B) with hardening authorization, but the question specifically asks for methods that harden against unauthorized access, which includes both authentication and authorization controls, and the correct answers (C and D) focus on authorization and mutual TLS authentication respectively.
Detailed technical explanation
How to think about this question
The NodeRestriction admission controller works by validating that a kubelet can only create/modify Node objects with a name matching its own node name and can only create/update Pod objects bound to its node. Under the hood, it uses the node's credentials (typically from a bootstrap token or client certificate) to enforce these constraints, preventing a compromised node from impersonating another node or modifying arbitrary pods. In a real-world scenario, without NodeRestriction, a malicious kubelet could delete pods on other nodes or alter node labels to disrupt scheduling.
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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this CKS question test?
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: Enable the NodeRestriction admission controller — Option C is correct because the NodeRestriction admission controller limits the Node and Pod objects a kubelet can modify, preventing a compromised node from escalating privileges or tampering with other workloads. This is a key Kubernetes-native control to harden the kubelet's authorization scope.
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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Last reviewed: Jun 30, 2026
This CKS practice question is part of Courseiva's free CNCF certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CKS exam.
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