IaaS stands for Infrastructure as a Service, and it is a cloud service model that provides customers with access to virtualized computing resources, such as servers, storage, and networks. In the IaaS model, the customer is responsible for patching the operating system (OS) of the virtual machines, as well as installing and managing the applications and dat a. The cloud service provider (CSP) is responsible for maintaining the physical infrastructure, such as the hardware, power, cooling, and security. Therefore, IaaS passes the responsibility of patching the OS to the customer, unlike PaaS, DBaaS, or SaaS, where the CSP handles the OS patching and updates. Reference: CompTIA Cloud+ CV0-003 Certification Study Guide, Chapter 2, Objective 2.1: Given a scenario, deploy cloud services and solutions.