Whonix (formerly known as TorBOX) is a Debian–based distribution which focuses on security. It aims to provide privacy, security and anonymity on the internet. This distribution consists of two virtual machines, a "Workstation" and a Tor "Gateway", running Debian GNU/Linux. All communications are forced through the Tor network to accomplish this.
For an openly developed, free and open-source software (FOSS), GPL licensed hypervisor that can run Whonix, it is recommended to use Kernel Virtual Machine (KVM) that comes with the GNU/Linux OS. KVM combined with the VirtualMachineManager front-end should provide a familiar, intuitive and easy-to-use GUI. KVM uses libvirt.