Virtualization: A double-edged sword

Virtualization became recently a hot topic once again, after being dormant for more than twenty years. In the meantime, it has been almost forgotten, that virtual machines are not so perfect isolating environments as it seems, when looking at the principles. These lessons were already learnt earlier when the first virtualized systems have been exposed to real life usage. Contemporary virtualization software enables instant creation and destruction of virtual machines on a host, live migration from one host to another, execution history manipulation, etc. These features are very useful in practice, but also causing headaches among security specialists, especially in current hostile network environments. In the present contribution we discuss the principles, potential benefits and risks of virtualization in a déjà vu perspective, related to previous experiences with virtualization in the mainframe era. 1 Introduction Recently, a vigorous interest in various virtualization techniques has been observed. Rather than being only a buzzword, virtualization became since 2005 a main direction in the evolution of the whole IT market. According to recent predictions by the Gartner Group, operating system virtualiza-tion and I/O virtualization will become mainstream by 2010 [1]. Traditionally, the leadership in providing virtualization based solutions belonged to IBM, beginning with the VM/370 operating system for System/370 mainframes introduced in 1972 [2]. With the advent of relatively cheap microprocessor based computers within the next decade, the IT industry shifted their interests to personal computing, based on individual hardware computers rather than some virtual machines. But at the beginning of the 21st century, most personal workstations and low-end servers became powerful enough to carry multiple operating systems running concurrently on the same hardware, which rised the interests in virtualization once again, this time on the commodity x86 platform. Moreover, it turned out from experience that setting up an extensive IT infrastructure with a lot of dedicated hardware put together with the appropriate, also dedicated software, is highly inefficient and also very expensive in management. Virtualization, leading generally to decoupling