Not long after midnight on 29 November 1985, a small group of guerillas belonging to the radical organisation Chukaku-ha, slashed the underground communications cables serving the Japan National Railways network in Tokyo and Osaka. They were protesting at government plans to privatise the railway system, but their action was perhaps more important for the way in which it focused attention on a quite different economic and social issue. In a single swift sortie, a handful of people had been able to prevent the movement of some 4.5 million computers, and bring the life of one of the world's largest cities to a temporary halt. Nothing could more effectively have demonstrated the great and growing dependence of contemporary social systems on the communication of information, not only between individual and individual, but also between computer and computer.