A public cloud is a form of cloud computing built on a multi- tenant environment, relying on a third-party cloud service provider for services such as applications, also known as Software as a Service (SaaS), and storage. Public cloud services are generally delivered over the Internet, are highly flexible, scalable and inexpensive, and may accommodate both prepaid or pay-per-use model. Some major cloud service providers are Amazon, Google, Microsoft, IBM, to name a few.