Qubes OS is a free and open-source security-oriented operating system meant for single-user desktop computing. Qubes OS leverages xen-based virtualization to allow for the creation and management of isolated virtual machines called qubes. Qubes, which are also referred to as domains or compartments, 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 which are based on popular operating systems such as Fedora, Debian or Windows. Levels of trust : from complete to non-existent. All windows are displayed in a unified desktop environment with unforgeable colored window borders so different security levels are easily identifiable.