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Windows administrators must maintain constant vigilance over their systems to prevent a vulnerability from crippling their systems or exposing data to threat actors. For shops that use Hyper-V, Microsoft offers another layer of protection through its virtualization-based security.
Virtualization-based security uses Hyper-V and the machine's hardware virtualization features to isolate and protect an area of system memory that runs the most sensitive and critical parts of the OS kernel and user modes. Once deployed, these protected areas can guard other kernel and user-mode instances.
Virtualization-based security effectively reduces the Windows attack surface, so even if a malicious actor gains access to the OS kernel, the protected content can prevent code execution and the access of secrets, such as system credentials. In theory, these added protections would prevent malware attacks that use kernel exploits from gaining access to sensitive information.
Code examining, malware prevention among key capabilities
Virtualization-based security is a foundation technology and must be in place before adopting a range of advanced security features in Windows Server. One example is Hypervisor-Enforced Code Integrity (HVCI), which examines code -- such as drivers -- and ensures the kernel mode drivers and binaries are signed before they load into memory. Unsigned content gets denied, reducing the possibility of running malicious code.
Other advanced security capabilities that rely on virtualization-based security include Windows Defender Credential Guard, which prevents malware from accessing credentials, and the ability to create virtual trusted platform modules (TPMs) for shielded VMs.
In Windows Server 2019, Microsoft expanded its shielded VMs feature beyond the Windows platform to cover Linux workloads running on Hyper-V to prevent data leakage when the VM is both static and when it moves to another Hyper-V host.
New in Windows Server 2019 is a feature called host key attestation, which uses asymmetric key pairs to authenticate hosts covered by the Host Guardian Service in what is described as an easier deployment method by not requiring an Active Directory trust arrangement.
What are the virtualization-based security requirements?
Virtualization-based security has numerous requirements. It's important to investigate the complete set of hardware, firmware and software requirements before adopting virtualization-based security. Any missing requirements may make it impossible to enable virtualization-based security and compromise system security features that depend on virtualization-based security support.
At the hardware level, virtualization-based security needs a 64-bit processor with virtualization extensions (Intel VT-x and AMD-V) and second-level address translation as Extended Page Tables or Rapid Virtualization Indexing. I/O virtualization must be supported through Intel VT-d or AMD-Vi. The server hardware must include TPM 2.0 or better.
System firmware must support the Windows System Management Mode Security Mitigations Table specification. Unified Extensible Firmware Interface must support memory reporting features such as the UEFI v2.6 Memory Attributes Table. Support for Secure Memory Overwrite Request v2 will inhibit in-memory attacks. All drivers must be compatible with HVCI standards.
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