The teenage creator of a variant of the Blaster worm that infected tens of thousands of computers in 2003 was sentenced to 18 months in prison on Friday, prosecutors said.

Jeffrey Lee Parson, 19, will spend 18 months in prison followed by a three-year supervised release program, and will be required to do 100 hours of community service, Judge Marsha Pechman ruled Friday in the U.S. District Court for the Western District of Washington. In addition, Pechman on Feb. 10 will determine how large a fine Parson will have to pay, according to a news release issued Friday by the U.S. Attorney for the Western District of Washington.

Parson created the W32.Blaster-B worm in August 2003, a few days after the original worm was first set loose on the Internet. He pleaded guilty to the charges in August 2004. The creator of the original worm has not been identified.

Both worms took advantage of flaws in Microsoft's Windows operating systems that allowed malicious hackers to take control of PCs. The Blaster worms instructed infected PCs to launch denial-of-service attacks on Microsoft's Windows Update Web site on certain dates.

Parson's variant used a file name that was identical to a domain name registered in his name. The U.S. Federal Bureau of Investigation was able to trace the domain name to computers owned by Parson at his Hopkins, Minnesota, home, where he was arrested days after his variant appeared.

Judge Pechman could have sentenced Parson to as long as 37 months in prison but chose the lighter sentence based on Parson's age, history of mental illness and lack of parental supervision, according to the statement distributed by prosecutors. The judge restricted him from using computers for anything but educational or business purposes, specifically forbidding video games and chat rooms.