What are thin hypervisors and are they more secure than other hypervisors?
Type 1 (bare-metal) hypervisors benefit virtual environments by serving as the only interface between virtualized workloads and the underlying hardware. There is no underlying operating system because the hypervisor acts as the OS for all practical purposes.
Thin hypervisors, on the other hand, are OS-independent, with the goal of running as efficiently as possible with minimal computing overhead. Minimizing the hypervisor also reduces the attack surface by limiting the number of ways malicious code could reach the hypervisor. Keeping the hypervisor simple helps keep it secure.
For example, VMware removed the console operating system from vSphere 5.1. Removing extra software reduces potential vulnerabilities. VMware claims this move makes the hypervisor much smaller, simplifies its deployment and reduces the need for patching.
The vendor also added two additional capabilities to address security. First, you can only install software with digital signatures on a vSphere host, which makes it almost impossible for unsigned software -- such as malware -- to make its way onto the virtual server. The hypervisor also includes application programming interfaces that enable monitoring and management without agents that could be compromised with malware.
This was first published in July 2013