1] Gary McKinnon
USA declared him as the biggest military computer hacker ever. He whacked the security system of NASA and Pentagon. This made him one of the great black hat hacker celebrities and got his name into the hacker's community. The nerd is now facing 70 years of imprisonment and is deprived from accessing internet. He has illegally accessed 97 computers and has caused around $700,000 damage to the economy.
2] Robert Tappan Morris
He is the creator of first internet worm ?Morris worm? he was a student at Cornell and from that where he started writing codes to create worms as he wanted to know how large the internet world is. But the worm lead to the slow speed of internet and made the systems no longer usable. There was no ways to know how many computers were affected but the experts alleged that around 6000 machines. He was sent to 3 years imprisonment, 400 hours of community service and was fined $10,500. At present he is a professor at Massachusetts institute of technology, computer science and artificial intelligence laboratory. He was the first person prosecuted under the 1986 Computer Fraud and Abuse Act.