Cloud computing is the most important technology at the present time, in terms of reducing applications costs and makes them more scalable and flexible. As the cloud currency is based on building virtualization technology, so it can secure a large-scale environment with limited security capacity such as the cloud. Where, Malicious activities lead the attackers to penetrate virtualization technologies that endanger the infrastructure, and then enabling attacker access to other virtual machines which running on the same vulnerable device. The proposed work in this paper is to review and discuss the attacks and intrusions that allow a malicious virtual machine (VM) to penetrate hypervisor, especially the technologies that malicious virtual machines work on, to steal more than their allocated quota from material resources, and the use of side channels to steal data and Passing buffer barriers between virtual machines. This paper is based on the Security Study of Cloud Hypervisors and classification of vulnerabilities, security issues, and possible solutions that virtual machines are exposed to. Therefore, we aim to provide researchers, academics, and industry with a better understanding of all attacks and defense mechanisms to protect cloud security. and work on building a new security architecture in a virtual technology based on hypervisor to protect and ensure the security of the cloud.