I. Introduction
Cyber systems have become an inseparable part of our everyday lives. During past decade the Internet has permeated business and leisure sectors. More recently critical infrastructures are beginning to shift from physical to cyber control, and in some cases interconnecting with public data networks, to gain function, efficiency and cost-effectiveness. At the same time cyber attacks continue to increase in frequency and severity. These emerging trends – the increase in cyber attacks and the increase in potential damage these may create in our everyday lives – make cyber defenses a top funding priority for US government and industry.