Despite its roots in the U. S. Department of Defense (DoD), the global Internet has primarily, although not exclusively, been an avenue and arena of peaceful commerce. With every year, an increasing percentage of the world's economy has migrated from physical media, or older electronic media such as telephones and telegraphs, to the public Internet and to private or semipublic internets. Systems that were once inaccessible to persons off-premises, such as power plant controls, are now theoretically accessible to anyone around the world. Other hitherto self-contained networks, such as those that transferred money, are now commingled with the larger, more public networks such as the Internet or the international phone system.

Indeed, its very success is what has turned the Internet into a potential venue of warfare. It is not only that defense systems of advanced militaries are being knit into more powerful systems of systems – thereby becoming the militaries' new center of gravity. The real impetus is that the more cyberspace is critical to a nation's economy and defense, the more attractive to enemies is the prospect of crippling either or both via attacks on or through it. Hackers can and do attack information systems through cyberspace. They can attack the cyberspace itself through operations against the networks that provide the basis for this new medium. Defenders thus must keep these hackers out of their systems. If hackers get in, they could wreak great damage. At a minimum they might steal information.