Jeffrey Lee Parson of Hopkins, Minn., last August pleaded guilty to unleashing the worm. Law enforcement officials said his Blaster variant infected more than 48,000 computers. It also unleashed a denial-of-service attack against Microsoft's web site.
The federal judge in Seattle who sentenced Parson reportedly said she was lenient on the teen because was immature for his age when he released the worm.
"Today's sentencing has sent a clear message that U.S. authorities are steadfast in their determination to take down virus writers and cybercriminals," said Gregg Mastoras, senior security analyst at antivirus supplier Sophos.