Shared Responsibility Model in Cloud Computing: Who Owns What?
In cloud computing, the shared responsibility model defines who is responsible for what across the layers of the stack. According to the shared responsibility model, which cloud computing service model you choose—Infrastructure as a Service (IaaS), Platform as a Service (PaaS), or Software as a Service (SaaS)—shapes the division of duties between the cloud provider and the customer. This division is essential for security, compliance, and operational resilience. As you move from raw infrastructure to a fully managed software solution, the provider takes on more of the platform and application stack, while the customer retains ownership of data, access governance, and risk management. Understanding these boundaries helps teams design robust controls, avoid blind spots, and communicate expectations to auditors and stakeholders.
What is the shared responsibility model?
The shared responsibility model is a practical map of accountability in cloud computing. It does not imply that one party can ignore security or governance; rather, it clarifies what each party must protect. For many organizations, this model translates into concrete actions such as configuring networks correctly, protecting data in transit and at rest, and managing identities and access. In cloud computing, the model also emphasizes continuous risk assessment and ongoing collaboration with the provider. By naming responsibilities up front, teams can align their security controls with regulatory requirements, operational needs, and business goals. When teams understand the shared responsibilities, they are better prepared to monitor, test, and improve their security posture in cloud computing environments.
IaaS, PaaS, and SaaS: where responsibilities lie
IaaS (Infrastructure as a Service)
Physical security of data centers, networking hardware, virtualization, storage, and the fundamental cloud infrastructure itself. They also manage availability, scalability, patching of the underlying hypervisor, and core security controls at the platform level. Protecting and managing the guest operating system, installed applications, data, and encryption keys. This includes configuring virtual networks and firewalls, applying patches to the OS and software, hardening workloads, securing access credentials, and monitoring for threats within the environment.
In IaaS, you own more control, but you also bear more responsibility for secure configuration and ongoing maintenance. The shared responsibility model becomes a practical guide for what you must document in security policies and audits, particularly around data protection, incident response, and vulnerability management in cloud computing.
PaaS (Platform as a Service)
The provider manages the runtime environment, middleware, operating system, virtualization, servers, storage, and the basic network controls. They ensure the platform stays up-to-date, secure, and scalable. Guarding and handling data, identity and access governance, application configuration, and security controls that sit on top of the platform. This includes securing APIs, managing secrets, and configuring robust logging and monitoring for the app layer.
With PaaS, the line shifts toward the application layer. The shared responsibility model still requires you to implement strong authentication, data encryption, and proper governance to prevent misconfigurations that could expose data or degrade service availability in cloud computing.
SaaS (Software as a Service)
The provider typically handles the entire stack up to and including the application itself, including application security, platform maintenance, and infrastructure hardening. They also manage data center security and core network protections. Managing data ownership, access control, user provisioning, and ensuring data quality and compliance with applicable regulations. Customers also need to monitor the use of the application, configure user roles responsibly, and back up their own data as needed.
In SaaS, the shared responsibility model places most of the responsibility on the provider, but accountability for data and access resides with the customer. This arrangement is common in productivity tools and line-of-business applications. Even so, organizations should configure security controls such as unique user accounts, role-based access, and data retention policies to maintain compliance in cloud computing environments.
Why the model matters for security and compliance
The shared responsibility model is not merely a theoretical framework; it directly affects risk management. When teams understand who is responsible for what, they can implement precise controls, reduce misconfigurations, and shorten incident response times. In cloud computing, misaligned responsibilities often manifest as insecure default settings, inadequate key management, or gaps in logging. By mapping controls to service models, organizations can design layered security that matches the actual threat landscape. Regulators and auditors frequently require evidence of this alignment, making the shared responsibility model a practical tool for demonstrating compliance in cloud computing environments.
Practical steps to apply the model effectively
Know which services you use (IaaS, PaaS, SaaS) and precisely who is responsible for each control in the stack. Enforce least privilege, role-based access, multi-factor authentication, and periodic access reviews to protect sensitive data and systems in cloud computing. Use encryption at rest and in transit where appropriate, and manage encryption keys with strong key management practices. Enable and centralize logs, set up alerts for anomalous activity, and retain logs for audits relevant to cloud computing governance. Translate regulatory requirements into concrete controls, and ensure those controls are tested regularly in your chosen service models. Define roles, runbooks, and escalation paths that reflect the shared responsibility model, so you can respond quickly when incidents occur in cloud computing environments.
Best practices for securing cloud workloads
Regardless of the service model you pick in cloud computing, these practices reinforce the shared responsibility model and help reduce risk. Start with a robust asset inventory, then implement automation to enforce configurations and drift detection. Emphasize data protection by default, apply encryption, and rotate keys regularly. Establish a strong IAM baseline, including privileged access management for administrators. Finally, invest in ongoing training so teams understand how to maintain security postures across IaaS, PaaS, and SaaS deployments. These steps bring the shared responsibility model to life, making cloud computing both secure and practical for day-to-day operations.
Common pitfalls and how to avoid them
In cloud computing, the provider is responsible for infrastructure and, depending on the service model, some platform or application components, but you remain accountable for data, access, and configurations that sit on top of the platform. Regularly audit and remediate misconfigurations that can arise as services evolve in cloud computing environments. Default security settings are not enough. You need customized controls aligned with your data sensitivity and regulatory needs. An effective plan requires cross-team coordination and clear ownership in the shared responsibility model.
Conclusion
The shared responsibility model remains a practical compass for navigating cloud computing. By clarifying who owns which controls across IaaS, PaaS, and SaaS, organizations can design resilient security and compliance programs without slowing innovation. The model encourages deliberate decisions about data protection, access governance, and operational practices, ensuring that security and governance scale alongside cloud adoption. In the end, embracing the shared responsibility model is not about shifting blame; it is about building a clearer, more reliable framework for cloud computing success that protects both the organization and its customers.
