Which method includes moving virtual machines from one physical server to another as a way to enhance security?

The correct answer is associated with the method of "MTD - Diversification," which involves moving virtual machines (VMs) among different physical servers as a security enhancement technique. The core idea behind diversification in this context is that by not allowing VMs to remain on a single host, the overall attack surface is reduced. This can help mitigate risks associated with vulnerabilities that may be present on a particular physical server or in the hypervisor software running on it.

Moving VMs to different servers also contributes to better resource utilization and load balancing. When VMs are diversified across various physical hosts, it’s more challenging for an attacker to exploit a single point of failure, thus promoting a more secure posture for the overall system.

Other concepts like shuffling, redundancy, and clustering have distinct focuses that do not primarily center on the enhanced security provided through the movement of VMs. For example, shuffling might refer to changing their positions without nuance to security; redundancy typically deals with duplicating components to ensure availability; and clustering relates to grouping multiple servers to work together as a single system but does not inherently address the proactive security measures provided by diversification.