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Bitdefender Napoca Hypervisor

The Bitdefender Napoca project is a lightweight type-1 hypervisor offering a solid foundation for building advanced security-focused functionality by providing control over the resources of a virtualized guest operating system. An example of such a project, originally built on top of Napoca, is the Hypervisor-based Memory Introspection.

Technology highlights

  • As a type-1 (bare-metal) hypervisor, Napoca offers control over - and can improve the security - of the primary operating system, from the start of the boot sequence
  • Hardware-assisted virtualization makes the CPU, memory, and all other hardware devices available to the guest operating system, guaranteeing top notch system performance
  • Allows interception of memory, MSR, IO, and control register resources based on instruction emulation with customizable behavior
  • Rich internal API, including memory management, guest memory management, CPU and virtual CPU management, guest to host communication, inter-processor communication, and advanced debugging
  • Can be deployed on UEFI and Legacy platforms by leveraging a provided UEFI loader or the GRUB boot loader
  • A userland DLL and a handy sample console application are provided to ease the interaction with the underlying hypervisor

Main project components

  1. Napoca - the actual hypervisor implementation
  2. Winguest - Windows user mode (winguestdll) and kernel mode (winguest) components for installing, configuring and interacting with the hypervisor
  3. Winguest_sample - user mode sample application built on top of the Winguest code to use as a starting point for developing new tools and showcase how to integrate the API
  4. EfiPreloader - a minimal and robust EFI loader application that can ease the adoption of UEFI Secure Boot by acting as a first stage loader to enable a custom chain of trust for the hypervisor (and the OS) boot flow
  5. EfiLoader - Napoca boot loader application for UEFI systems

Building and Running

The project supports only the Microsoft Visual Studio build toolchain under Windows.


  • Visual Studio 2019
    • Workloads
      • Desktop Development with C++
    • Individual components [recommended to leave already checked options enabled]
      • MSVC v142 - VS 2019 C++ x64/x86 Spectre-mitigated libs (v14.XX) [version must match the version of an equivalent selected unmitigated lib]
      • C++ ATL for latest v142 build tools with Spectre Mitigations (x86 & x64)
      • Windows 10 SDK (10.0.18362) [1903]
  • Windows 10 WDK 10.0.18362 [1903]
  • NASM
    • make sure it is added to the system PATH variable
  • Powershell 5.0 or later [should already be installed if using Windows 10]
    • Enable powershell scripts: powershell.exe as Admin -> Set-ExecutionPolicy Unrestricted -> [A] Yes to All
  • Python 3
    • py -3 -m pip install PyYAML
  • Doxygen [optional, only required if generating html/latex documentation]


  • Full Build dacia.sln using desired platform and configuration options (e.g., x64 - Release)

Create deployable package

  • ./deploy_binaries.ps1 -Platform x64 -Configuration Release -Destination .\install [customize as needed]


  • Disable secure boot on the target machine (if enabled)
  • Copy the 'install' folder obtained previously to the target machine (Following commands assume the folder was copied to c:\dacia)
  • Run winguest_sample.exe as Administrator
    • drvinstall C:\dacia\install\driver\winguest.inf {8a5531a8-2c02-482e-9b2e-99f8cacecc9d}\BdWinguest
    • drvconnect
    • setpath 1 C:\dacia\install\hv\
    • setpath 2 C:\dacia\install\hv\updates_intro\
    • setpath 3 C:\dacia\feedback\
    • config enable
  • Reboot


  • Run winguest_sample.exe as Administrator
    • drvconnect
    • queryhv
    • help to see more available commands


  • You can use a debug console over serial by using config enable serial in winguest_sample and attaching a serial cable on the onboard COM port. Type help to see available commands. Note that you might need to uninstall the Windows serial drivers so that it will not try to use the COM port as well.
  • We have a failsafe that will disable the hypervisor after 3 boot attempts without also loading the user mode components. See winguest_sample commands setfailcnt and resetfailcnt for more details.


The entire Bitdefender Napoca team.


Lightweight type-1 hypervisor offering a foundation for building advanced security-focused functionality.





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