Attack Trends

The early days The origins of VMs go back almost as far as modern computing itself. Born to optimize usage of expensive computing resources and provide users with a fully dedicated and interactive computer system, the early 1960s experiences in time-sharing systems at MIT, IBM, Bolt Beranek and Newman (now BBN Technologies), and the University of California, Berkeley, laid the foundations on which VMs were developed. Memory protection, segmentation and paging, virtual memory and storage, the implementation of microprocessors with multiple execution modes, and the needs arising from multiple users multi-programming on a single computing system all hastened the development of time-sharing systems, such as the Compatible Time-Sharing System at MIT. In time, this system led to Multics (Multiplexed Information and Computing Service) and eventually to modern-day Unix operating systems (OSs); the same foundational concepts from those early systems (www.bitsavers.org/ pdf/mit/lcs/tr/MIT-LCS-TR-003. pdf ) led to the creation of the IBM System/360 family of computers in the 1960s and to the System/370 in the early 1970s. Current VM concepts derive from these pioneering systems—in fact, the CP/CMS OS developed at IBM (later reimplemented and renamed VM/370) provided the same functional components found in today’s most popular virtualization software. The control program (CP), which controlled allocation and isolation, and managed the computing resources for multiple VMs, is functionally equivalent to today’s VM monitors (VMMs), the systems required to implement a generic VM environment. The conversational monitor system (CMS) is a full-fledged singleuser OS that supports personal use of a dedicated (virtual) computer, the equivalent of a “guest” OS in a modern VM environment. Communications between users on different VMs were first accomplished in VM/370 by using an underlying directory structure that the CP managed but were later assimilated into the design goals of a dedicated OS, the remote spooling and communications system (RSCS), which was capable of running on a VM. In 1981, at the dawn of the PC era, R.J. Creasy provided an insightful account of the origins of VM/370 in IBM’s Journal of Research and Development and its potential future application for personal computing. Today, the z/VM operating system that runs on zSeries of IBM mainframe is a direct descendant of VM/370.