The XTS-400 is a multilevel secure computer operating system. It is multiuser and multitasking that uses multilevel scheduling in processing data and information. It works in networked environments and supports Gigabit Ethernet and both IPv4 and IPv6. The XTS-400 is a combination of Intel x86 hardware and the Secure Trusted Operating Program (STOP) operating system. XTS-400 was developed by BAE Systems, and originally released as version 6.0 in December 2003.