‘Cloud computing’ has been embraced more than ever before due to a number of obvious advantages (e.g. elasticity, space-saving, hardware consolidation and cost-saving) over traditional computing infrastructure. Virtualization is the core part of cloud computing as it provides a multi-tenancy model which is the foundation of cloud computing. Typically there are two types of threats inherent with virtualization environments. One wildly noticed threat is vm-escape which means a user on a virtual machine can ‘Escape’ from it and take control over the whole hypervisor. The other threat known as inter-vm attacks have often been overlooked by the research community.