Virtualization is one of the main components of the cloud. The traffic between vSwitches goes invisible, making it a sweet spot for hackers. Virtualization can also be viewed as having invisible, miniature data centers that include virtual switches (vSwitches) The answer is to deploy that much-required visibility to monitor inter-vSwitch traffic as you would with other network traffic. With the advanced persistent threat approach, attackers watch and wait for such opportunities. The answer to this is to use a virtual appliance that sits on the virtual layer and is able to monitor and prevent threats.”]
Source: https://securityintelligence.com/cloud-security-virtualization-vswitches-blind-spot/