How to secure Virtual Servers in Data Centers

Nowadays, virtual servers are the new normal for the efficient utilization of hardware computing resources in Data Centers. While discussing virtual servers' requirements and security with server administrators, they generally hard to accept any security risks in virtual servers.

I am trying to list security risks and corresponding mitigations. This list I am using this while doing virtualization security assessments.

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Risks	Mitigation
Unmanaged VMs	Documentation of Virtualization infrastructure is the key. If the admin document the virtualization architecture, it is very easy to identify unmanaged VMs while auditing.
Unpatched Hypervisor	Identify the version of the virtualization infrastructure and patched it. Patch management policy should be documented and implement.
Misconfigured services	Disable services that are not required. Configuration management should be documented.
User Management	Effective control policy should be there for user creation and deletion.
Performance issues in VMs	Internal periodic performance review is required to assess resource requirement by each VMs
Data loss on VM failiure	Data backup policy should be documented and implemented properly.
Uncontrolled provisioning and deprovisioning of new VMs	Proper policy should be documented and implemented for provisioning and de-provisioning of VMs
Sensitive data in VMs	Encryption and logging is the key. Use cryptography techniques to secure data. Logging critical events. Must understand the proper balance between security and performance.
Easy cloning of VMs	Control creation, storage, and use of VMs by documenting the process and implement.
Leaking of data in motion	Use of secure protocols while transmission of data between VMs.

Conclusion

Virtualization is a great technology, but it will be a risk if not used with utmost care. Use a security benchmark for the hardening of virtual infrastructure. Virtualization management policy documentation is the key to secure data centers.