Understanding the Cloud Security Paradigm

Cloud security operates on fundamentally different principles than traditional on-premises infrastructure. The shared responsibility model divides security obligations between cloud providers and customers, but this division varies by service type and implementation details. Understanding these boundaries is crucial for effective threat modeling, as assumptions about provider responsibilities can leave dangerous gaps in security coverage.

In Infrastructure as a Service (IaaS), customers bear responsibility for everything from the operating system up, while providers secure the physical infrastructure and hypervisor. Platform as a Service (PaaS) shifts more responsibility to providers, but customers still must secure their applications and data. Software as a Service (SaaS) places most security burden on providers, though customers retain responsibility for access management and data classification. These models create different threat landscapes that threat modeling must address.

Multi-tenancy introduces unique threats where customer resources share underlying infrastructure. While providers implement strong isolation, vulnerabilities like CPU side-channel attacks (Spectre, Meltdown) demonstrate that perfect isolation remains elusive. Threat modeling must consider both the protections providers implement and the residual risks of shared infrastructure. The "noisy neighbor" problem extends beyond performance to potential security implications.

The API-driven nature of cloud platforms creates new attack surfaces. Every action in the cloud typically involves API calls that must be authenticated and authorized. These APIs expose powerful capabilities—a single API call might delete entire databases or expose storage buckets to the internet. Traditional network-centric security models fail in environments where API access provides the primary control plane.