Isolation in Public Clouds: Threats, Challenges, and DefensesMany applications that are in day to day use by customers over the Internet are hosted in the public clouds. Public clouds such as Amazon EC2, Google Compute Engine and Microsoft Azure allow clients to run virtual machines (VMs) on shared physical infrastructure. This practice of multi tenancy improves efficiency by multiplexing resources among disparate customers at low costs. Unfortunately, it also introduces the risk of sharing a physical server to