Securing the cloud – why shared responsibility matters

Too many businesses use the cloud assuming their provider completely handles security. It is an incorrect assumption, and one that sits behind many of today’s most damaging data breaches, compliance failures and operational breakdowns.

The truth is simple. Cloud providers secure the cloud infrastructure. You secure what you put in it.

That is the foundation of the shared responsibility model, but it is one of the most widely misunderstood concepts in cloud security. And misunderstanding it leaves gaps that attackers are ready to exploit.

This article breaks it down clearly and practically. You will learn how the shared responsibility model works across different service types, where your responsibilities start and stop, the mistakes that most often lead to incidents, and how to embed this model into your operations, governance and culture. Get it right, and you build a foundation that lets you scale securely, move faster and stay in control. Get it wrong and you are exposed.

The shared responsibility model defines how security responsibilities are split between the cloud service provider and the customer. This is not just a theoretical concept – it is a practical framework that guides how organisations manage security in the cloud.

The balance of responsibility shifts depending on the service model:

Infrastructure as a Service (IaaS) – The provider secures the physical infrastructure, networking and virtualisation layers. The customer is responsible for everything above that including: the operating system, applications, identities, data, logical network configurations and security monitoring of services.

Platform as a Service (PaaS) – The provider manages more of the stack, including the operating system, runtime and middleware. The customer is responsible for the security of application logic, data protection, managing user access and security monitoring.

Software as a Service (SaaS) – The provider manages almost the entire technology stack – from infrastructure through to the application itself. The customer remains responsible for identity and access management, data security and monitoring of application tier and user behaviour, including detecting suspicious activities.

Many organisations mistakenly believe that cloud security is entirely the provider’s responsibility. It is not, and assuming it is does not just create risk, it creates a false sense of safety that leaves critical gaps.

Here’s a simplified breakdown: 

Most cloud security incidents are not caused by flaws in the cloud itself. They stem from a failure to understand the model.

Misconfigured storage like AWS S3 buckets or Azure blobs set to allow public access remains one of the most common mistakes. Others include over-permissioned accounts or weak identity controls, poor data classification or encryption, missing incident response plans for cloud workloads and blind spots in third-party SaaS or shadow IT environments. These are not cloud provider failures. They are governance failures, and they are preventable.

For chief technology officers (CTOs), chief information officers (CIOs) and chief information security officers (CISOs), securing the cloud is not simply about buying the right tools. What matters most is having a clear understanding of your responsibilities – and adopting a modern operating model that embeds security into how the organisation works.

Here’s what needs to happen – starting now:

Operationalise the shared responsibility model – This cannot just sit in documentation. It needs to become live knowledge across engineering, DevOps and security teams. Build it into your cloud operating model, including onboarding, architecture reviews and audit readiness.

Map responsibilities to security domains – Clearly define what is customer-managed, provider-managed and shared. Use this as the foundation for your policies, contracts, service level agreements and compliance processes.

Enable cross-cloud visibility – Use tools and processes that give real-time visibility across all cloud environments – Microsoft Azure, Amazon Web Services (AWS), Google Cloud Platform (GCP) and other software as a service (SaaS) vendors. Cloud-native security services like Microsoft Defender for Cloud as multi-cloud monitoring and protection services should feed directly into your security information and event management (SIEM) system, for continuous visibility and security posture management.

Establish policy-driven governance – Enforce security standards through automated policies and controls. Use infrastructure as code (IaC) and continuous integration/continuous deployment (CI/CD) pipelines to make secure and policy-driven configuration part of every deployment, not something added later.

Educate and align your teams – Cloud responsibility is not a niche skill. It needs to be embedded across all teams. Security is no longer a silo, it is a shared competency that underpins how you scale safely.

In the cloud, what you assume is someone else’s responsibility often becomes your biggest risk. The shared responsibility model is not just a technical framework – it is a blueprint for trust, resilience and operational excellence.

Leaders who drive this clarity, and bake it into governance and technical execution will enable their organisations to scale securely, adapt faster and stay in control in an ever-changing threat landscape.

Ready to embed the shared responsibility model into your cloud strategy? Let’s talk.