It has been described as “amazing”, “groundbreaking” and “impressive” by computer-security specialists. The Stuxnet worm, a piece of software that infects industrial-control systems, is remarkable in many ways. Its unusual complexity suggests that it is the work of a team of well-funded experts, probably with the backing of a national government, rather than rogue hackers or cyber-criminals (see article). It is designed to infect a particular configuration of a particular type of industrial-control system — in other words, to disrupt the operation of a specific process or plant. The Stuxnet outbreak has been concentrated in Iran, which suggests that a nuclear facility in that country was the intended target.