The cloud shared responsibility model defines which security tasks belong to the cloud provider and which remain with the customer. The provider secures the underlying cloud infrastructure, while the customer secures identity, configurations, data, workloads, and access controls across IaaS, PaaS, and SaaS services.
What the shared responsibility model means in practice
The cloud shared responsibility model is not a single security control, it is an operating boundary. It defines which protections are built into the provider’s platform and which protections must be implemented, maintained, and validated by the customer.
That boundary shifts by service model. IaaS typically leaves more configuration and hardening work to the customer, while SaaS moves more responsibility to the provider but still leaves customers accountable for users, permissions, content, and governance.
Why the boundary matters for security outcomes
The model matters because many cloud incidents come from mismatched assumptions about who was supposed to secure what. If a team assumes the provider handles identity, configuration, logging, or data protection end to end, gaps can persist even when the underlying cloud platform is functioning as designed.
It also changes how organisations think about control ownership. The provider may secure the service infrastructure, but the customer still has to manage access decisions, conditional exposure, tenant configuration, encryption choices, and the protection of sensitive data and workloads.
How the model differs across IaaS, PaaS, and SaaS
In IaaS, the customer usually carries the larger share of operating responsibility, including operating system hardening, network controls, workload configuration, and many aspects of identity and application security. In PaaS, some of that burden shifts to the service, but secure use of the platform still depends on customer-side configuration and entitlements. In SaaS, the provider owns more of the application stack, yet the customer still controls administration, data sharing, access governance, and the way the tenant is configured.
This is why the same control can sit on different sides of the boundary in different services. Logging, key management, identity, backup, and monitoring may be partly provider-operated and partly customer-governed depending on the service and the contract.
What organisations should use the model to clarify
The shared responsibility model is most useful when it is turned into a control-ownership map for each cloud service in use. That map should make it obvious who configures access, who reviews logs, who responds to misuse, who manages data protection settings, and who is accountable for each layer of the stack.
It is also a good lens for procurement and architecture review. If a service description does not clearly spell out provider versus customer obligations, especially around identity, logging, and data handling, the organisation should treat that as an unresolved security requirement rather than an implementation detail.
Risk and Threat Considerations
Misunderstanding the responsibility split can leave critical gaps in access control, logging, hardening, and data protection. Attackers often benefit when customers assume the cloud provider is monitoring or securing a layer that actually remains the customer’s obligation.
Failure mechanism: A service is deployed with insecure defaults, weak permissions, or missing tenant-level monitoring because no one has explicitly accepted ownership for the control.
Impact: The result can be exposed data, uncontrolled administrative access, missed detection of malicious activity, and slower incident response across cloud workloads and SaaS tenants.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
CSA Cloud Controls Matrix, NIST SP 800-53 Rev 5 and NIST CSF 2.0 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| CSA Cloud Controls Matrix | IAM — Identity & Access Management | Cloud shared responsibility directly allocates identity and access duties between provider and customer. |
| Recommendation — Map identity and access duties to IAM so each cloud service has explicit owner-controlled access governance. | ||
| NIST SP 800-53 Rev 5 | AC-2 — Account Management | The model requires customers to own account lifecycle and access administration in cloud services. |
| CM-2 — Baseline Configuration | Cloud shared responsibility hinges on who hardens and maintains service configuration baselines. | |
| AU-2 — Audit Events | The model depends on clear ownership for logging and audit visibility across provider and customer layers. | |
| Recommendation — Assign cloud account lifecycle ownership and review access paths under AC-2. Establish and maintain cloud configuration baselines under CM-2 for each service model. Define required cloud audit events and verify who collects and reviews them under AU-2. | ||
| NIST CSF 2.0 | GV.OC-01 — Organizational Context | Shared responsibility clarifies which cloud security duties sit with the organisation versus the provider. |
| Recommendation — Document cloud control ownership in governance so each service has an accountable party. | ||
Practitioner Guidance
Why practitioners should care: The model is only useful if it is translated into concrete ownership. For cloud programs, that means treating shared responsibility as a control-design problem, not a documentation exercise, so every major service has a named owner for configuration, access, logging, and recovery.
What to watch for: Ambiguous vendor documentation, inconsistent assumptions between security and platform teams, and control gaps that appear at service boundaries are all signs that the responsibility split has not been fully operationalised.
Practitioner takeaway: The safest cloud environments are not those with the most provider guarantees, but those where customer obligations are explicitly mapped, tested, and continuously reviewed.
Related resources from NHI Mgmt Group
- Guide: Cloud Security Guide
- Shared Responsibility Model
- Who is responsible for securing cloud workloads in a shared responsibility model?
- What should organisations do when the cloud shared responsibility model makes data protection harder to assign to one team?
- How should security teams apply the shared responsibility model after migrating sensitive data to the cloud?