Qubes OS is a security-oriented, Fedora-based desktop Linux distribution whose main concept is "security by isolation" by using domains implemented as lightweight Xen virtual machines.
Why does Qubes use Xen?
Qubes OS is an operating system which uses the Xen hypervisor to provide strong security for desktop computing through isolated virtual machines.
What version of Linux is Qubes?
Qubes release 4.1. 2-rc1
For important work, we recommend the latest stable release.