The nation’s health, wealth, and security rely on the production and distribution of certain goods and services. The array of physical assets, processes and organizations across which these goods and services move are called critical infrastructures (e.g. electricity, the power plants that generate it, and the electric grid upon which it is distributed). Computers and communications, themselves critical infrastructures, are increasingly tying these infrastructures together. This report aims to address the concern that this reliance on computers and computer networks raises the vulnerability of the nation’s critical infrastructures to “cyber” attacks.