The Shared Responsibility Model Explained: Who Secures What in AWS, Azure, and GCP?

Migrating to the cloud is not a lift-and-shift of security responsibilities. One of the most critical—and often misunderstood—concepts in cloud security is the Shared Responsibility Model. This framework defines the security obligations of the cloud provider and those of you, the customer.

Misunderstanding this model is a primary cause of data breaches in the cloud. The rule of thumb is simple: The cloud provider is responsible for the security of the cloud, while the customer is responsible for security in the cloud.

This guide will demystify the Shared Responsibility Model, provide a clear breakdown for the major providers (AWS, Azure, GCP), and outline the practical steps you must take to secure your share of the responsibility.

What is the Shared Responsibility Model?

The Shared Responsibility Model is a security and compliance framework that delineates the boundary between the cloud provider’s security obligations and the customer’s security obligations. It ensures that every aspect of the cloud environment is secured, but without duplication of effort.

The division of responsibility changes depending on the service model you use: Infrastructure as a Service (IaaS), Platform as a Service (PaaS), or Software as a Service (SaaS).

The Provider’s Responsibility: Security OF the Cloud

The cloud provider (AWS, Azure, Google Cloud) is always responsible for protecting the underlying infrastructure that runs all the services offered in the cloud. This includes:

• Physical Security: Securing the data centers, hardware, cabling, and power.
• Network Infrastructure: Securing the global network backbone, routers, switches, and load balancers that interconnect their services.
• Hypervisor & Host Operating System: Ensuring the security of the virtualization layer that isolates customer instances from each other and the host.
• Core Cloud Services: The foundational compute, storage, database, and networking services themselves.

In simple terms, if a cloud provider manages the hardware, software, or network component, they are responsible for its security, patching, and defense against threats.

The Customer’s Responsibility: Security IN the Cloud

Your responsibility is governed by a fundamental principle: the more control you have, the more responsibility you bear. This encompasses everything you put on top of the cloud provider’s foundational services.

• Customer Data: The number one responsibility. You are always responsible for classifying, encrypting, protecting, and managing access to your own data.
• Identity and Access Management (IAM): Managing users, groups, roles, and permissions. This includes enforcing principles like Least Privilege and Multi-Factor Authentication (MFA).
• Platform, Application, & Identity Management: Securing your operating system, network configurations, and applications you deploy.
• Client-Side & Server-Side Data Encryption: Managing encryption keys and encrypting data at rest and in transit.
• Network Security Configurations: Configuring security groups, firewall rules, network ACLs, and virtual networks.
• Compliance: Ensuring your use of the cloud service complies with relevant industry regulations (GDPR, HIPAA, PCI DSS).

How Responsibility Shifts by Service Model

The key to understanding the model is visualizing how the customer’s burden of management and security changes based on the abstraction level.

1. Infrastructure as a Service (IaaS) – Most Customer Responsibility

• Examples: AWS EC2, Azure Virtual Machines, Google Compute Engine.
• Analogy: Renting a plot of land (the cloud) and building your own house. The landlord provides the land and utilities, but you are responsible for the building, locks, and everything inside.
• Customer Manages: Operating System, Applications, Data, Runtime, IAM, Network Controls.
• Provider Manages: Physical Network, Physical Security, Hypervisor, Host OS.

2. Platform as a Service (PaaS) – Shared Responsibility

• Examples: AWS Elastic Beanstalk, Azure App Service, Google App Engine.
• Analogy: Renting a fully built apartment. The landlord maintains the building structure, plumbing, and electricity. You are responsible for your belongings and locking your apartment door.
• Customer Manages: Applications, Data, IAM.
• Provider Manages: Runtime, Operating System, Network Controls, Hypervisor, Physical Security.

3. Software as a Service (SaaS) – Least Customer Responsibility

• Examples: Salesforce, Office 365, Gmail, AWS Aurora Serverless.
• Analogy: Staying in a hotel. The hotel manages the building, your room, furniture, and utilities. You are only responsible for your personal belongings and who you invite into the room.
• Customer Manages: Data (and who has access to it), IAM.
• Provider Manages: Everything else: Applications, Runtime, OS, Network, Hypervisor, Physical Security.

A Comparative Look: AWS, Azure, and GCP

While the core principle is identical across all major providers, their graphical representations and terminology differ slightly.

Provider	Their Terminology & Focus
AWS	Uses the classic “Shared Responsibility Model” diagram. Heavily emphasizes the differentiation between IaaS/PaaS/SaaS. Their model is often considered the industry benchmark.
Microsoft Azure	Framed around the “Division of Responsibility.” Azure places a strong emphasis on identity as the primary security perimeter and integrates its model tightly with its well-developed identity solutions (Active Directory).
Google Cloud (GCP)	Often uses the term “Shared Fate” to encourage a deeper partnership, suggesting providers should offer tools and best practices to help customers meet their responsibilities. GCP emphasizes security by default.

Crucial Takeaway: Despite minor differences in presentation, the fundamental division of security tasks remains consistent across all three platforms.

Best Practices for Managing Your Responsibility

Knowing your responsibility is one thing; managing it effectively is another.

1. Leverage Provider Security Tools: Use native tools like AWS IAM, Azure Security Center, and Google Cloud Security Command Center to gain visibility and enforce policies.
2. Embrace “Infrastructure as Code” (IaC): Use templates (AWS CloudFormation, Azure ARM, GCP Deployment Manager) to define and deploy secure, repeatable configurations, eliminating manual errors.
3. Automate Compliance Scanning: Continuously scan your cloud environment for misconfigurations using tools like AWS Config, Azure Policy, or GCP Security Health Analytics.
4. Implement a Strong IAM Foundation: Enforce MFA everywhere, follow the principle of least privilege, and avoid using root/administrator accounts for daily tasks.
5. Encrypt Everything by Default: Encrypt data at rest and in transit. Manage your encryption keys carefully using services like AWS KMS, Azure Key Vault, or Google Cloud KMS.

Conclusion: Shared Responsibility is a Partnership

The Shared Responsibility Model is not a way for cloud providers to shift blame; it is a framework for enabling agility and scale while maintaining security. The cloud’s security is a shared partnership.

The provider gives you a secure foundation and powerful tools, but it is your responsibility to use them correctly. The most secure cloud environment is one where both parties understand and perfectly execute their roles. By internalizing this model, you can build and operate in the cloud with confidence, knowing your assets are protected from the data center floor to the application layer.

Understanding your responsibilities is the first step. Now, learn how to implement them with our guide to Cloud Security Posture Management (CSPM) and master access control with Identity and Access Management (IAM) in the Cloud.