Episode 78 — Cloud Security I: Shared Responsibility Model
In Episode Seventy-Eight, “Cloud Security Part One: Shared Responsibility Model,” we explore the foundational principle that governs every secure cloud deployment—the clear understanding of who is responsible for what. Moving to the cloud does not eliminate accountability; it redistributes it. Security becomes a partnership between the cloud provider, who manages the physical and foundational layers of the environment, and the customer, who configures, operates, and secures what runs atop those layers. Without clarity in this relationship, even the most advanced technologies can leave dangerous gaps where each party assumes the other is in control. The shared responsibility model exists to close those gaps before they become incidents.
At its core, this model draws a line between provider and customer obligations, but the exact location of that line shifts depending on the service model. Cloud providers guarantee the security of the cloud, encompassing the underlying infrastructure—data centers, networks, and hardware—while customers are responsible for the security in the cloud, meaning their configurations, data, identities, and code. This division must be understood not just in policy documents but in daily operational behavior. When both sides act on accurate assumptions, risks are managed coherently; when they don’t, trust fragments and vulnerabilities multiply unnoticed.
Different service types—Infrastructure as a Service, Platform as a Service, and Software as a Service—represent degrees of that shared responsibility. Under Infrastructure as a Service, or I a a S, the provider secures the core infrastructure, but customers manage operating systems, applications, and all access controls. Platform as a Service, or P a a S, relieves customers of operating system and runtime management but still leaves them accountable for application logic, data security, and identity design. Software as a Service, or S a a S, pushes most technical security to the provider, yet customers remain responsible for user behavior, data governance, and permission settings. The higher the abstraction, the less control you hold—but never zero responsibility.
Data governance remains firmly on the customer side of the line regardless of model. Cloud providers ensure the durability and availability of storage systems, but they do not determine which data is sensitive or how it is handled. Classification, labeling, and access restrictions must still come from the customer’s internal governance program. Encrypting data, enforcing retention policies, and ensuring proper disposal of obsolete information are part of this duty. Whether the data sits in a virtual machine disk, a managed database, or a third-party SaaS application, the obligation to identify and protect it always remains with its owner.
Identity management serves as another critical shared layer where confusion often leads to breaches. Providers deliver the identity infrastructure—authentication engines, role-based access controls, and integration frameworks—but customers define who can access what and under what conditions. Assigning roles, enforcing multifactor authentication, and rotating credentials all fall under the customer’s domain. Many cloud compromises trace back not to technical flaws in the platform but to misconfigured permissions or overprivileged accounts. Clear role design and periodic access reviews translate shared responsibility from theory into practical control.
Network configuration is another domain where responsibility shifts subtly but decisively. The provider secures the physical links, routers, and hypervisor-level segmentation that form the cloud’s backbone. The customer configures virtual networks, subnets, and firewalls that determine how workloads interact. Failing to restrict open ports or leaving administrative interfaces exposed is not a cloud failure—it is a configuration failure. Proper network design mirrors on-premise principles: minimize exposure, separate environments by sensitivity, and enforce least privilege between tiers. Shared responsibility does not remove these fundamentals; it merely changes the tools used to apply them.
The compute layer represents an equally balanced partnership. The provider maintains the physical hosts and hypervisors, while customers control the operating systems, applications, and patches within their virtual machines. Even in managed environments, customers must ensure that custom images are hardened and regularly updated. Neglecting patch management under the assumption that “the provider handles it” remains one of the most frequent misunderstandings leading to cloud breaches. The shared model functions best when customers treat compute resources with the same diligence they would in their own data centers—because in many ways, they still own them.
Storage systems in the cloud exemplify how shared responsibility extends across data protection and lifecycle. Providers guarantee the persistence of stored objects, but customers decide who can access them and whether encryption is enabled. Misconfigured access controls—such as public buckets or permissive shared links—are among the most common exposure events in cloud environments. Encryption at rest and in transit, coupled with well-defined retention and deletion policies, forms the customer’s obligation. Providers make these capabilities available, but activating and governing them is entirely the customer’s choice—and responsibility.
Logging and monitoring follow a similar pattern. Cloud providers supply mechanisms to capture logs, metrics, and alerts, but customers must enable, store, and analyze them. Turning on logging features without planning retention, correlation, or alerting creates only the illusion of visibility. Each party contributes to observability: providers ensure infrastructure logs are trustworthy, and customers ensure application and account activity is recorded and reviewed. Compliance frameworks often require proof of log integrity and retention, responsibilities that sit squarely with the cloud tenant.
Key management exemplifies one of the most sensitive intersections between customer control and provider infrastructure. Providers can offer managed encryption keys, customer-supplied keys, or hybrid options. The choice determines who holds ultimate control. Using provider-managed keys simplifies operations but gives the platform authority over rotation and lifecycle. Customer-managed keys add complexity but preserve ownership and separation of duties. Selecting the right model requires understanding regulatory and operational requirements. Whichever option is chosen, the responsibility for protecting keys—and by extension, encrypted data—never disappears; it only changes form.
Many organizations also rely on third-party integrations within their cloud ecosystems. These external services often inherit or extend provider controls, but that inheritance must be verified, not assumed. Each integration introduces its own configuration, authentication, and data handling practices. Understanding where these external boundaries lie—and how they interact with your core environment—prevents gaps where trust is implied but not enforced. Shared responsibility extends beyond the provider to every connected entity that processes or stores your data.
Contracts and service-level agreements, or S L A s, provide the formal expression of this model. They define uptime commitments, incident response responsibilities, and specific security expectations. Reading and negotiating these documents carefully ensures that assumptions become enforceable terms. Clauses covering breach notification, data residency, and access to audit reports form the practical backbone of shared accountability. If responsibilities are not written down, they are not guaranteed. Clear contracts protect both sides from misinterpretation and make security expectations traceable over time.
Finally, independent audits and attestations—such as SOC 2, ISO 27001, or FedRAMP certifications—allow customers to verify that the provider meets its declared responsibilities. Reading these reports critically, rather than accepting them as blanket assurance, helps customers map which controls are covered by the provider and which remain their duty. A strong shared responsibility program continuously cross-references provider attestations with internal compliance requirements. This mapping turns trust into verification, ensuring that security oversight extends as far as the partnership itself.
The shared responsibility model thrives on clarity and execution. Providers secure their platforms; customers secure their workloads; and both communicate transparently when changes occur. Confusion over boundaries leads to breaches, while well-defined cooperation builds confidence. The most resilient cloud environments are those where roles are understood, documented, and lived out in daily operations. In that clarity, shared responsibility becomes more than a diagram—it becomes a durable framework for secure, scalable collaboration in the cloud.
