Who Is Responsible for Security in Azure PaaS?
A company deploys a custom web application on Azure App Service (PaaS). The application stores user data in Azure SQL Database. The security team is responsible for securing the application code, managing authentication, and configuring TLS for data in transit. According to the Microsoft shared responsibility model, which security responsibility remains with Microsoft for this PaaS deployment?
Quick Answer
The answer is Microsoft remains responsible for patching the operating system of the underlying physical and virtual hosts. This is correct because the shared responsibility model for PaaS draws a clear line: the cloud provider secures the host infrastructure, including the hypervisor and host OS, while the customer secures everything they deploy on top of it, such as application code, authentication, and TLS configuration. On the SC-900 exam, this distinction is frequently tested to ensure you understand that PaaS does not mean the customer is off the hook for application-level security, nor does it mean Microsoft manages the customer’s data or code. A common trap is assuming Microsoft handles database-level patching or application runtime updates, but those remain customer responsibilities in PaaS. To remember this, think of the “host vs. guest” split: Microsoft owns the host OS patches; you own the guest application and its data.
⚠ Common exam trap
Watch out — candidates often assume 'data at rest encryption' is entirely Microsoft's responsibility in PaaS, but the shared responsibility model requires customers to manage key rotation, access policies, and compliance for encryption, making it a shared task rather than a sole Microsoft responsibility.
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
✓
Patching the operating system of the underlying physical and virtual hosts
In a PaaS deployment like Azure App Service, Microsoft is responsible for the security of the underlying cloud infrastructure, including patching the operating system of the physical and virtual hosts that run the platform. This is a core tenant of the shared responsibility model, where the customer manages application-level security (code, authentication, TLS) while Microsoft manages the host OS and hypervisor.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Patching the operating system of the underlying physical and virtual hosts
Why this is correct
In PaaS, Microsoft is responsible for maintaining and patching the host OS and infrastructure, freeing the customer from managing these layers.
- ✗
Configuring the firewall rules for the web application
Why it's wrong here
Firewall rules for the web application (e.g., Azure App Service access restrictions) are customer-managed to control inbound and outbound traffic.
- ✗
Managing user access to the application
Why it's wrong here
User authentication and authorization are application-level responsibilities managed by the customer using Microsoft Entra ID or other identity systems.
- ✗
Encrypting the application data at rest in Azure SQL Database
Why it's wrong here
While Microsoft provides transparent data encryption (TDE) for Azure SQL Database, the customer can choose to use it and manage encryption keys, making encryption at rest a shared or customer responsibility depending on configuration.
Go deeper
Related to this question
Learn chapter
Core Security Concepts
Key term
SQL
SQL is a standard programming language used to manage, query, and manipulate relational databases by issuing commands like SELECT, INSERT, UPDATE, and DELETE.
Key term
Tenant
A dedicated and isolated instance of Microsoft Entra ID that an organization receives when signing up for a Microsoft cloud service.
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Same concept, more angles
3 more ways this is tested on SC-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 deploys a custom web application on Azure App Service (PaaS). The application stores data in Azure SQL Database. The security team needs to identify which security responsibilities fall under the customer according to the Microsoft shared responsibility model. Which of the following is primarily the customer's responsibility for this PaaS deployment?
hard- A.Physical security of the datacenter hosting the App Service
- B.Patching the operating system of the App Service host machines
- ✓ C.Managing user identities and access to the application
- D.Network security for the Azure backbone connecting datacenters
Why C: In a PaaS deployment like Azure App Service with Azure SQL Database, the customer is responsible for managing user identities and access to the application, including authentication, authorization, and role-based access control (RBAC). Microsoft manages the underlying infrastructure, including the host OS, physical datacenter security, and network backbone, but the customer must secure application-level access and data plane operations.
Variation 2. A company deploys a custom application on Azure App Service (PaaS). Which of the following security responsibilities falls completely under the customer's scope according to the shared responsibility model?
hard- A.Applying operating system patches to the virtual machines running the App Service
- B.Configuring network security groups to filter traffic to the App Service
- ✓ C.Managing the application code and its configuration
- D.Ensuring physical security of the Azure data centers
Why C: In the shared responsibility model for PaaS like Azure App Service, the customer is responsible for managing the application code and its configuration, including secrets, connection strings, and authentication settings. Microsoft manages the underlying platform, including the OS and runtime, so the customer's scope is limited to what they deploy and configure within the service.
Variation 3. A company is deploying a web application on Azure App Service. The security officer states that according to the shared responsibility model, the customer is responsible for managing access to the application and securing the application code. Which of the following responsibilities does Microsoft retain for Azure App Service?
hard- A.Configuring network firewall rules for the App Service
- ✓ B.Patching the underlying operating system of the App Service host
- C.Managing user authentication and authorization
- D.Applying encryption to the application data at rest
Why B: For Azure App Service, Microsoft retains responsibility for patching the underlying operating system of the host infrastructure. This is part of the shared responsibility model where the cloud provider manages the host OS and hypervisor, while the customer manages the application code, data, and access configurations.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SC-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 SC-900 exam.