Which security control is a shared responsibility within the Software as a Service (SaaS) model?

In the Software as a Service (SaaS) model, the shared responsibility revolves around the security of the application itself, which includes the design, development, and management of the software that users access over the internet. In this model, the service provider is primarily responsible for securing the overall infrastructure that supports the application, including the physical and network layers, while the customer holds responsibility for managing the data within the application, such as its classification, access controls, and user permissions.

Regarding the application, customers also have a role in ensuring that they use the application securely, which may include implementing appropriate authentication methods, managing user roles and permissions, and understanding how the application integrates with other services. Therefore, the security of the application is a shared responsibility because it involves collaboration between the service provider and the user.

In contrast, platform and infrastructure security are typically more managed by the service provider, and while data security is a critical concern for users, in the context of the SaaS model, it reflects the user's responsibility rather than a shared one. Thus, the application security control stands out as the area where both parties play essential roles, making it the correct answer.