Enabling multi-level security in a single-level security computing system with the use of a virtual operating system executed using a virtualisation tool

595860 Disclosed is a system for enabling multi-level security. A mass storage device is operable to be coupled to one or more processors. The mass storage device includes a base operating system (26) which is operable to be executed by the processors and implements a single security level. The storage device also includes a virtual operating system (16) which is operable to be executed by the processors and executed using a virtualization tool (28) executed by the base operating system (26). The virtual operating system (16) is operable to process information according to a plurality of security levels and communicate the information to one or more computing systems (12). The information is communicated according to the plurality of security levels of the information.