Question 374 of 981
Shared Responsibility Model in IaaS: What Microsoft Handles
A company is migrating a legacy customer relationship management (CRM) application to Azure infrastructure as a service (IaaS). The application runs on Windows Server and uses a third-party database. The company's IT team will manage the application and database software. However, they want to minimize their operational overhead for tasks that Azure can handle automatically. According to the shared responsibility model, which of the following tasks is the responsibility of Microsoft?
Quick Answer
The answer is replacing a failed physical hard disk drive in the Azure data center. This is correct because under the shared responsibility model for IaaS, Microsoft manages the physical infrastructure—including servers, storage, networking, and the data center itself—while the customer retains control over the operating system, applications, and data. In an IaaS deployment, you are responsible for everything you install or configure on the virtual machine, such as the Windows Server OS, the third-party database, and the CRM application, but you never have access to the underlying hardware. On the Microsoft Azure Fundamentals AZ-900 exam, this concept tests your understanding of where the responsibility boundary lies: the cloud provider handles the “physical” layer, and the customer handles the “logical” layer. A common trap is assuming Microsoft patches the guest OS or manages the database, but those are customer tasks in IaaS. Remember the memory tip: “Microsoft owns the floor and the walls; you own the furniture and the software inside the room.”
⚠ Common exam trap
It's easy for candidates to confuse 'operational overhead' with 'security updates' or 'network configuration,' mistakenly thinking Azure handles all management tasks, but the shared responsibility model clearly separates physical infrastructure (Microsoft) from customer-managed software and configuration.
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
✓
Replacing a failed physical hard disk drive in the Azure data center.
In the shared responsibility model, Microsoft is responsible for the 'physical' aspects of the cloud, including the hardware, network, and data center infrastructure. Replacing a failed physical hard disk drive is a physical infrastructure task that falls under Microsoft's responsibility, as the customer has no access to the underlying hardware in an IaaS environment.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Applying security updates to the CRM application code.
Why it's wrong here
Incorrect. The customer is responsible for managing and patching the application code because it is deployed and maintained by the customer on the virtual machine.
When this WOULD be correct
This would be correct in a PaaS or SaaS scenario, such as when using Azure App Service or Azure SQL Database, where Microsoft manages the platform and applies security updates to the application runtime or database software.
- ✗
Configuring firewall rules within the virtual network.
Why it's wrong here
Incorrect. Customers manage network security configurations, such as network security group rules and firewall settings, for their virtual networks in IaaS.
When this WOULD be correct
In a PaaS scenario where the customer uses Azure SQL Database or Azure App Service, Microsoft manages the underlying network and firewall rules at the platform level, making this a Microsoft responsibility.
- ✓
Replacing a failed physical hard disk drive in the Azure data center.
Why this is correct
Correct. Microsoft manages the physical hardware in Azure data centers, including replacement of failed components like hard drives. This is part of the infrastructure responsibility.
- ✗
Installing the latest Windows Server security patches on the virtual machine.
Why it's wrong here
Incorrect. Under IaaS, the customer is responsible for maintaining the operating system, including applying security patches, updates, and configuration management.
When this WOULD be correct
If the question were about a PaaS service like Azure App Service or Azure SQL Database, where Microsoft manages the underlying OS and platform, then installing security patches would be Microsoft's responsibility.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The AZ-900 exam frequently reuses these exact scenarios with slightly different constraints.
✓Replacing a failed physical hard disk drive in the Azure data center.Correct answer▾
Why this is correct
Correct. Microsoft manages the physical hardware in Azure data centers, including replacement of failed components like hard drives. This is part of the infrastructure responsibility.
✗Applying security updates to the CRM application code.Wrong answer — click to see why▾
Why this is wrong here
In the shared responsibility model for IaaS, Microsoft is responsible for the physical infrastructure, not the application code. Applying security updates to the CRM application is the customer's responsibility.
★ When this WOULD be the correct answer
This would be correct in a PaaS or SaaS scenario, such as when using Azure App Service or Azure SQL Database, where Microsoft manages the platform and applies security updates to the application runtime or database software.
Why candidates choose this
Candidates may mistakenly think that because Microsoft provides the cloud service, they also handle application-level security updates, confusing IaaS with PaaS or SaaS responsibilities.
✗Configuring firewall rules within the virtual network.Wrong answer — click to see why▾
Why this is wrong here
Configuring firewall rules within the virtual network is a customer responsibility because the customer manages network configurations in IaaS, even though Microsoft maintains the underlying network infrastructure.
★ When this WOULD be the correct answer
In a PaaS scenario where the customer uses Azure SQL Database or Azure App Service, Microsoft manages the underlying network and firewall rules at the platform level, making this a Microsoft responsibility.
Why candidates choose this
Candidates may confuse network security tasks with Microsoft's responsibility for physical security, or assume that since Microsoft provides the network, it also manages all firewall rules.
✗Installing the latest Windows Server security patches on the virtual machine.Wrong answer — click to see why▾
Why this is wrong here
In the shared responsibility model for IaaS, Microsoft is responsible for the physical infrastructure, while the customer manages the guest OS, including security patches. Installing Windows Server security patches on the VM is the customer's responsibility.
★ When this WOULD be the correct answer
If the question were about a PaaS service like Azure App Service or Azure SQL Database, where Microsoft manages the underlying OS and platform, then installing security patches would be Microsoft's responsibility.
Why candidates choose this
Candidates may confuse IaaS with PaaS or think that Microsoft handles all security updates, not realizing that in IaaS the customer manages the guest OS and applications.
Analysis generated from the official AZ-900blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Same concept, more angles
1 more way this is tested on AZ-900
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company subscribes to a SaaS-based customer relationship management (CRM) application hosted in the cloud. The CRM provider manages the application, runtime, and infrastructure. The company's employees access the CRM via a web browser. According to the shared responsibility model, which security responsibility belongs solely to the company?
medium- A.Patching the underlying operating system of the CRM servers.
- B.Managing network access controls to the CRM application.
- ✓ C.Safeguarding the company's customer data and user identities.
- D.Ensuring physical security of the data centers hosting the CRM.
Why C: In a SaaS model, the provider manages the application, runtime, and infrastructure, including patching the OS and physical security. The customer retains responsibility for what they bring into the cloud: their data and user identities. Option C is correct because safeguarding customer data and managing user identities (e.g., via Azure AD) is solely the company's responsibility under the shared responsibility model.
Last reviewed: Jun 11, 2026
This AZ-900 practice question is part of Courseiva's free Microsoft 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 AZ-900 exam.
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