- A
Use a firewall to block all ports except those required
Why wrong: Firewalls can block access, but the service itself remains running and could be exploited if accessed from within.
- B
Apply a NetworkPolicy to block traffic to the node
Why wrong: NetworkPolicy controls pod-to-pod traffic, not node services.
- C
Identify and disable unnecessary system services using systemctl or similar tools
Disabling and removing unnecessary services reduces the attack surface directly.
- D
Use AppArmor to confine the services
Why wrong: AppArmor confines the service but does not remove it; the service still runs.
Question 88 of 997
Disabling Unnecessary Services for Node Hardening
This CKS practice question tests your understanding of system hardening. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 node in your cluster is running unnecessary services that increase the attack surface. Which of the following is the BEST approach to reduce the attack surface on the node?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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
✓
Identify and disable unnecessary system services using systemctl or similar tools
Option C is correct because the most direct way to reduce the attack surface on a node is to disable unnecessary services that are actively listening or running. Tools like `systemctl disable` or `systemctl stop` permanently turn off services such as `telnet`, `rpcbind`, or `cups`, which are common vectors for exploitation. Simply blocking ports with a firewall (A) leaves the service running and potentially exploitable via localhost or if the firewall is misconfigured, while AppArmor (D) confines but does not remove the service. NetworkPolicies (B) operate at the Kubernetes network layer and cannot control host-level services.
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.
- ✗
Use a firewall to block all ports except those required
Why it's wrong here
Firewalls can block access, but the service itself remains running and could be exploited if accessed from within.
- ✗
Apply a NetworkPolicy to block traffic to the node
Why it's wrong here
NetworkPolicy controls pod-to-pod traffic, not node services.
- ✓
Identify and disable unnecessary system services using systemctl or similar tools
Why this is correct
Disabling and removing unnecessary services reduces the attack surface directly.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use AppArmor to confine the services
Why it's wrong here
AppArmor confines the service but does not remove it; the service still runs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
A common mistake in the CKS exam is to focus on network-level controls (firewall, NetworkPolicy) or confinement (AppArmor) rather than disabling the unnecessary service directly. The key is that disabling the service removes the attack surface entirely, whereas blocking or confining still leaves the service running and potentially exploitable through other means.
Detailed technical explanation
How to think about this question
Under the hood, disabling a service with `systemctl disable` removes its symlink from `/etc/systemd/system/multi-user.target.wants/`, preventing it from starting on boot, while `systemctl stop` sends a SIGTERM to the process. This is critical because services like `rpcbind` (port 111) or `avahi-daemon` (port 5353) are often enabled by default in cloud images and have known CVEs (e.g., CVE-2017-8779 for rpcbind). In a real-world scenario, a CIS benchmark for Kubernetes nodes explicitly requires disabling services such as `cups`, `telnet`, and `NFS` to comply with Level 1 hardening standards.
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 practitioner preparing for the CKS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Quick reference
OSI Model Reference
| Layer | Name | PDU | Key Protocols / Devices |
|---|---|---|---|
| 7 | Application | Data | HTTP, HTTPS, DNS, SMTP, FTP, SSH |
| 6 | Presentation | Data | TLS / SSL, JPEG, ASCII encoding |
| 5 | Session | Data | NetBIOS, RPC, SIP |
| 4 | Transport | Segment / Datagram | TCP, UDP |
| 3 | Network | Packet | IP, ICMP, OSPF — Routers |
| 2 | Data Link | Frame | Ethernet, Wi-Fi, PPP — Switches, Bridges |
| 1 | Physical | Bits | Cables, NICs, Hubs, Repeaters |
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.
- →
System Hardening — study guide chapter
Learn the concepts, then practise the questions
- →
System Hardening practice questions
Targeted practice on this topic area only
- →
All CKS questions
997 questions across all exam domains
- →
Certified Kubernetes Security Specialist CKS study guide
Full concept coverage aligned to exam objectives
- →
CKS practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related CKS practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Monitoring Logging and Runtime Security practice questions
Practise CKS questions linked to Monitoring Logging and Runtime Security.
Cluster Setup and Hardening practice questions
Practise CKS questions linked to Cluster Setup and Hardening.
System Hardening practice questions
Practise CKS questions linked to System Hardening.
Minimize Microservice Vulnerabilities practice questions
Practise CKS questions linked to Minimize Microservice Vulnerabilities.
Supply Chain Security practice questions
Practise CKS questions linked to Supply Chain Security.
Monitoring, Logging and Runtime Security practice questions
Practise CKS questions linked to Monitoring, Logging and Runtime Security.
Cluster Setup practice questions
Practise CKS questions linked to Cluster Setup.
Cluster Hardening practice questions
Practise CKS questions linked to Cluster Hardening.
CKS fundamentals practice questions
Practise CKS questions linked to CKS fundamentals.
CKS scenario practice questions
Practise CKS questions linked to CKS scenario.
CKS troubleshooting practice questions
Practise CKS questions linked to CKS troubleshooting.
Practice this exam
Start a free CKS practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
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: Identify and disable unnecessary system services using systemctl or similar tools — Option C is correct because the most direct way to reduce the attack surface on a node is to disable unnecessary services that are actively listening or running. Tools like `systemctl disable` or `systemctl stop` permanently turn off services such as `telnet`, `rpcbind`, or `cups`, which are common vectors for exploitation. Simply blocking ports with a firewall (A) leaves the service running and potentially exploitable via localhost or if the firewall is misconfigured, while AppArmor (D) confines but does not remove the service. NetworkPolicies (B) operate at the Kubernetes network layer and cannot control host-level services.
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.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Keep practising
More CKS practice questions
- Which flag is used to restrict the kubelet's ability to modify node status and pods?
- A Falco rule has priority `WARNING` and output: `Sensitive file opened (user=%user.name command=%proc.cmdline file=%fd.n…
- Falco detects a shell being opened inside a container. Which Falco rule field is used to specify the syscall condition f…
- A security audit reveals that a ServiceAccount named 'monitor' has a ClusterRoleBinding to the cluster-admin role. What…
- Match each Kubernetes security component to its description.
- Match each Kubernetes certificate type to its usage.
Last reviewed: Jul 4, 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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.