Qubes OS is a free and open-source, security-oriented operating system for single-user desktop computing. Qubes OS leverages Xen-based virtualization to allow for the creation and management of isolated compartments called qubes.
These qubes, which are implemented as virtual machines (VMs), have specific:
Purposes: with a predefined set of one or many isolated applications, for personal or professional projects, to manage the network stack, the firewall, or to fulfill other user-defined purposes.
Natures: full-fledged or stripped-down virtual machines based on popular operating systems, such as Fedora, Debian, and Windows.
Levels of trust: from complete to non-existent. All windows are displayed in a unified desktop environment with unforgeable colored window borders so that different security levels are easily identifiable.