computers around the world most of them in iran. the worm interfered with the operations of centrifuges in the natanz enrichment plant in iran one thousand centrifuges were affected fifteen to thirty percent of iran s enrichment capacity most experts suspect that the u.s. was behind the attack although some say it may also have been israel. in december twenty fifth teen western ukraine was hit by a power failure hundreds of thousands of people were affected in what turned out to be the first successful hacker attack on a power grid the attackers managed to break into the grids network system and then just before christmas they disconnected several substations the result blackout. russia was widely believed to have organized the attack. in spring