We can categorise the types of services offered by cloud service providers into several buckets based upon the nature of the offering. The wide variety of services available in the cloud are often described as “*anything as a service*,” or the acronym **XaaS**, where X indicates the nature of the specific service. ### Infrastructure as a Service (**IaaS**) Infrastructure as a service (IaaS) offerings allow customers to *purchase and interact with the basic building blocks of a technology infrastructure*. These include computing, storage, and networks. Customers then have the flexibility to configure and manage those services in any way they like to meet their own business needs. The customer doesn't need to worry about the management of the underlying hardware, but they do have the ability to customise components to meet their needs. In the IaaS model, the cloud service provider is responsible for managing the physical facilities and the underlying hardware. The market is currently dominated by three major players: Amazon Web Services (**AWS**), Microsoft **Azure**, and Google Cloud Platform (**GCP**). ### Software as a Service (**SaaS**) Software as a service (SaaS) offerings provide customers with *access to a fully managed application running in the cloud*. The provider is responsible for everything from the operation of the physical datacenters to the performance management of the application itself, although some of these tasks may be outsourced to other cloud service providers. In the SaaS model, the customer is only responsible for limited configuration of the application itself, the selection of what data they wish to use with the cloud solution, and the use of application-provided access controls to limit access to that data. The SaaS model is widely used to deliver applications ranging from **web-based email** to enterprise resource planning (**ERP**) and customer relationship management (**CRM**) suites. ### Platform as a Service (**PaaS**) Platform as a service (PaaS) offerings fit into a *middle ground between SaaS and IaaS solutions*. In a PaaS offering, the service provider offers a platform where customers may run applications that they have developed themselves. The cloud service provider builds and manages the infrastructure and offers customers an execution environment, which may include code libraries, services, and tools that facilitate code execution. Function as a service (**FaaS**) platforms are an example of PaaS computing. This approach allows customers to *upload their own code* functions to the provider and then the *provider will execute those functions* on a scheduled basis, in response to events, and/or on demand. The AWS Lambda service is an example of a FaaS/PaaS offering. Because FaaS environments do not expose customers to the actual server instances executing their code, they are often referred to as *serverless computing environments*. However, this is **somewhat of a misnomer**, since FaaS environments most certainly do have servers running the code, but they do so in a manner that is transparent to the FaaS customer. >[!important] Managed Services >Organisations may also choose to outsource some or all of the management of their technology infrastructure. Managed service providers (**MSPs**) are services organisations that provide information technology as a service to their customers. > >MSPs may *handle an organisation's IT needs completely, or they may offer focused services* such as network design and implementation, application monitoring, or cloud cost management. MSPs are not necessarily cloud service providers themselves (although they may be both MSP and CSP). > >They are typically capable of working across a customer's total environment, including both cloud and on-premises deployments. > >When MSPs offer security services, they are commonly referred to as managed security service providers (**MSSPs**). Services offered by MSSPs include *security monitoring*, *vulnerability management*, *incident response*, and *firewall management*.