Hardware/server virtualization is commonly employed in cloud computing to enable ubiquitous access to shared system resources and provide sophisticated services. The virtualization is typically performed by a hypervisor, which provides mechanisms that abstract hardware and system resources from the operating system. However, hypervisors are complex software systems with many vulnerabilities. This chapter analyzes recently-discovered vulnerabilities associated with the Xen and KVM open-source hypervisors, and develops their attack profiles in terms of hypervisor functionality (attack vectors), attack types and attack sources. Based on the large number of vulnerabilities related to hypervisor functionality, two sample attacks leveraging key attack vectors are investigated. The investigation clarifies the evidence coverage for detecting attacks and the missing evidence needed to reconstruct attacks.