- A
The company, because patches for underlying infrastructure are always the customer's responsibility in EC2.
Why wrong: This is incorrect. While customers are responsible for managing the guest operating system on EC2 instances, the underlying infrastructure, including the host OS, is managed by AWS as part of 'Security of the Cloud'.
- B
AWS, because the hypervisor and host OS are part of the 'Security of the Cloud'.
Correct. AWS is responsible for protecting the infrastructure that runs all AWS services, including the host OS, hypervisor, physical servers, and networking. Patching the host OS falls under this responsibility.
- C
The company, because EC2 is an Infrastructure as a Service (IaaS) offering and the customer manages the OS.
Why wrong: This is a common misunderstanding. Although customers manage the guest OS on EC2 instances, the host OS is part of the underlying cloud infrastructure and is managed by AWS. The customer's OS management responsibility is limited to the guest OS.
- D
Both the company and AWS share responsibility equally for host OS patching.
Why wrong: This is incorrect. Responsibility is not equal; it is clearly divided. AWS manages the host OS, and the customer manages the guest OS. There is no shared responsibility for patching the host OS.
Quick Answer
The answer is AWS, because the host operating system falls under the "Security of the Cloud" portion of the shared responsibility model. AWS is responsible for patching the host OS—the operating system that runs the hypervisor and manages the physical hardware—since customers have no access or control over it. This distinction is critical: the customer only patches the guest OS (the OS inside the EC2 instance) and any applications, while AWS secures the underlying infrastructure. On the AWS Certified Cloud Practitioner CLF-C02 exam, this concept often appears as a trick question where the scenario mentions "host OS patching" to test whether you know the boundary between customer and AWS responsibilities. A common trap is assuming the customer patches everything on EC2, but remember: if you cannot log into it, AWS handles it. For a quick memory tip, think "Host = AWS, Guest = Me"—the host OS is the invisible layer AWS maintains, while your guest OS is your domain.
CLF-C02 Cloud Concepts Practice Question
This CLF-C02 practice question tests your understanding of cloud concepts. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 company has deployed a web application on Amazon EC2 instances. The company's security team wants to ensure that the underlying host operating system is patched against a newly discovered vulnerability. According to the AWS Shared Responsibility Model, who is responsible for applying the patch to the host operating system?
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
AWS, because the hypervisor and host OS are part of the 'Security of the Cloud'.
Under the AWS Shared Responsibility Model, AWS is responsible for the security of the cloud, which includes the physical infrastructure, hypervisor, and host operating system that runs EC2 instances. When a vulnerability is discovered in the host OS (the OS that runs the hypervisor and manages the physical hardware), AWS must apply the patch because the customer has no access to or control over the host OS. The customer is only responsible for patching the guest OS (the OS running inside the EC2 instance) and any applications deployed on it.
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 company, because patches for underlying infrastructure are always the customer's responsibility in EC2.
Why it's wrong here
This is incorrect. While customers are responsible for managing the guest operating system on EC2 instances, the underlying infrastructure, including the host OS, is managed by AWS as part of 'Security of the Cloud'.
- ✓
AWS, because the hypervisor and host OS are part of the 'Security of the Cloud'.
Why this is correct
Correct. AWS is responsible for protecting the infrastructure that runs all AWS services, including the host OS, hypervisor, physical servers, and networking. Patching the host OS falls under this responsibility.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The company, because EC2 is an Infrastructure as a Service (IaaS) offering and the customer manages the OS.
Why it's wrong here
This is a common misunderstanding. Although customers manage the guest OS on EC2 instances, the host OS is part of the underlying cloud infrastructure and is managed by AWS. The customer's OS management responsibility is limited to the guest OS.
- ✗
Both the company and AWS share responsibility equally for host OS patching.
Why it's wrong here
This is incorrect. Responsibility is not equal; it is clearly divided. AWS manages the host OS, and the customer manages the guest OS. There is no shared responsibility for patching the host OS.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates mistakenly apply the IaaS model's general rule (customer manages the OS) to the host OS, forgetting that in virtualized EC2, the host OS is part of the hypervisor layer managed solely by AWS.
Detailed technical explanation
How to think about this question
The host operating system runs directly on the physical hardware and hosts the Xen or Nitro hypervisor, which isolates and manages EC2 instances. AWS uses a 'bare metal' style of patching where the host OS is updated without customer intervention, often through live migration or instance reboots that AWS schedules. In contrast, the customer must patch the guest OS (e.g., Amazon Linux, Windows Server) using tools like AWS Systems Manager Patch Manager or manual updates, as AWS has no access to the instance's OS.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this CLF-C02 question test?
Cloud Concepts — This question tests Cloud Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: AWS, because the hypervisor and host OS are part of the 'Security of the Cloud'. — Under the AWS Shared Responsibility Model, AWS is responsible for the security of the cloud, which includes the physical infrastructure, hypervisor, and host operating system that runs EC2 instances. When a vulnerability is discovered in the host OS (the OS that runs the hypervisor and manages the physical hardware), AWS must apply the patch because the customer has no access to or control over the host OS. The customer is only responsible for patching the guest OS (the OS running inside the EC2 instance) and any applications deployed on it.
What should I do if I get this CLF-C02 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 11, 2026
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