host OS.
When you put all this together, you have the ability to create a secure VM
environment that is protected from any level of administrator (when using TPM 2 in
the host) and will close a security hole many environments cannot close today.
Separation of duties and sphere of influence is critical with shielded VMs and the Host
Guardian Service. The HGS must not be within the influence of the virtualization
administrators nor the regular Active Directory administrators. For this reason, in
most environments, the HGS, which runs as its own physical cluster in its own Active
Directory forest, can also then be physically separated (completely) from the rest of
the servers. Think of a separate locked cage within the datacenter containing the
physical HGS cluster that is accessible from only the specific HGS administrators who
are completely separate from the other administrative roles. This means that to get to
data, there would have to be collusion between separate roles such as the
virtualization administrator and the HGS administrator. There is minimal benefit to
deploying shielded VMs if the HGS runs as a VM under the management of the very
people from whom it is designed to protect, unless you simply wish to encrypt the
disks at rest for compliance purposes. You also can use local guardians only instead of
an HGS. However, with local guardians, there is no health attestation, and only the
guardian’s private key is required, which can be found in the local certificate store.
The benefit of local guardians is that they can work on the Standard edition, whereas
guarded VMs that leverage HGS must run on hosts (known as guarded hosts) running
the Datacenter SKU.
Two types of guarded VMs are running in a guarded fabric:
Shielded VMs The full protection and restrictions discussed earlier in this section
providing full protection for the VMs from the fabric administrators
Encryption Supported VMs Supports the vTPM and uses BitLocker to encrypt
the content of the storage along with the hardened VM worker process. Other
restrictions such as no console access and no integration services are not enabled
by default but can be configured per item.A good way to think about which type to use is as follows: If you don’t trust the fabric
nor the administrators, you should use a shielded VM. If the fabric and the
administrators are fully trusted in the environment, such as a corporate private cloud,
and only encryption-at-rest is required for compliance reasons without impeding
administration via console connections and PowerShell Direct, then use encryption-
supported VMs.
Host Guardian tools are available that are installed by adding the RSAT-Shielded-VM-
Tools RSAT component. One of the tools is the Shielding Data File Wizard
(shieldingdatafilewizard .exe), which helps create the necessary data file that can
be used to shield VMs and as part of shielded VM templates.
Deploying Shielded VMs