Who would have thought a youth misspent playing Space Invaders and Donkey Kong could prepare you for the real world? Certainly not Mikko Hypponen's father, who, seeing no future in computers and frustrated by his son's obsession with them, sometimes resorted to desperate measures. "He removed the fuse in my bedroom to turn the electricity off, just to get me to come to the dinner table," says Hypponen.

But as it turned out, the hours spent taking on alien invaders served as training for battling an altogether different kind of assailant: computer viruses. Hypponen, now the chief research officer of the Finnish computer security firm F-Secure, has become one of the most respected virus hunters in the business.