History

In the 1980s the United States Department of Defense provided guidelines and requirements for establishing data processing security in its computer installations. These criteria, as specified in Department of Defense Trusted Computer System Evaluation Criteria, DoD 5200.28-STD (also known as TCSEC or the Orange Book), applied also to the computer systems in companies working with a government contract. The criteria corresponded to a particular security designation, depending on the type and amount of security the system provides. The security designations ranged from D (the least amount of security) through C1, C2, B1, B2, B3, and A1. The National Security Agency (NSA) performed a formal evaluation to determine whether a data processing system adhered to the guidelines and requirements for a given security designation.

Between 1988 and 1990 IBM® enhanced MVS™, RACF®, JES2, JES3, TSO, VTAM®, DFP, and PSF to meet the B1 criteria. MVS/ESA Version 3 Release 1 Modification Level 3 passed the formal evaluation performed by the National Security Agency and obtained a B1 security designation. For several years, subsequent versions of RACF, MVS/ESA, and OS/390® were designed to continue to meet the B1 criteria, although no formal evaluations were done. But over time new functions such as UNIX System Services were added to MVS that could not be used on a system with a B1 security designation. And customer configurations evolved to require networking, which could not be used on a B1 system. Eventually the Common Criteria and ISO 15408 superseded the older US Government standards described in the Orange Book.

IBM's multilevel security functions for z/OS® build on the work done on MVS to meet the B1 criteria, and provide functions consistent with those described in the Common Criteria and some of the Common Criteria Protection Profiles.

Although the requirements for multilevel security arose from the classified data processing needed by government installations, the functions implemented for multilevel security (especially the basic ones of user and data classification via security labels) should be relevant to commercial installations too.