The advent of virtualization technologies has evolved the IT infrastructure and organizations are migrating to virtual platforms. Virtualization is also the foundation for cloud platform services. Virtualization is known to provide more security into the infrastructure apart from agility and flexibility. However security aspects of virtualization are often overlooked. Various attacks to the virtualization hypervisor and its administration component are desirable for adversaries. The threats to virtualization must be rigorously scrutinized to realize common breaches and knowing what is more attractive for attackers. In this thesis a current state of perimeter and operational threats along with taxonomy of virtualization security threats is provided. The common attacks based on vulnerability database are investigated. A distribution of the virtualization software vulnerabilities, mapped to the taxonomy is visualized. The famous industry best practices and standards are introduced and key features of each one are presented for safeguarding the virtualization environments. A discussion of other possible approaches to investigate the severity of threats based on automatic systems is presented.