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IT Essentials — Assessing Infrastructure and Networks

customized applications without the necessity of housing the infrastructure. In this case, the IaaS
provider, such as Amazon Web Services (AWS), Microsoft, Google, or IBM, provides a platform on
which organizations can quickly develop their applications.

Platform as a Service (PaaS) — provides hardware and software tools (platform) for creating
software and applications. This cloud service model is suitable for organizations that want to host
and run applications in the cloud without having to manage the infrastructure (i.e., storage, updates,
O/S). Providers of PaaS include, among others, Microsoft Google, and AWS.

Software as a Service (SaaS) — an application delivered through the cloud available over the
internet, usually for a set fee. This model allows the greatest flexibility to the recipient organization.
Providers of SaaS include Google Apps, Netsuite, Salesforce.com, ServiceNow, Workday, Dropbox,
and DocuSign, among others.

In a traditional “on-premise” model, the organization is responsible for all aspects of the network,
including owning and maintaining all servers, storage, OSs, and developing and maintaining
applications. Cloud-based services offer an alternative to this model.

According to National Institute of Standards and Technology (NIST), “cloud computing is a model for
enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable
computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly
provisioned and released with minimal management effort or service provider interaction” through
the internet.

In this model, an organization engages a third-party provider to offer cloud-based services. A cloud-
based architecture can combine or simplify some of the network relationships, and offers flexibility
for the cloud service recipient.

Typical Cloud Architecture by Type and Responsibility
Source: IIA GTAG: “IT Essentials for Internal Auditors”

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