HIERARCHICAL APPROACH TO COMPUTER SYSTEM INTEGRITY

Security is an important factor if the programs of independent and possibly error-prone or malicious users are to coexist on the same computer system. In this paper, it is shown that a hierarchically structured operating system, such as produced by a virtual machine system, that combines a virtual machine monitor with several independent operating systems (VMM/OS), provides substantially better software security than a conventional two-level multiprogramming operating system approach. This added protection is derived from redundant security using independent mechanisms that are inherent in the design of most VMM/OS systems. Such a system can be obtained by exploiting existing software resources.