A US teenager who wrote the Blaster-B worm, which infected around 48,000 computers worldwide and caused hundreds of thousands of pounds of damage to businesses, has been jailed for 18 months.
The Minnesota man was also sentenced to 10 months' community service when he is released.
Blaster-B burst onto the scene in August 2003 with a successful denial of service attack on the Microsoft website.
The Blaster-B worm, a modification of the more damaging Blaster-A worm that infected many more users in 2002, sparked an international hunt by the FBI for the virus writer.
"An 18-month prison sentence is probably the best that this man could have realistically hoped for," said Graham Cluley, senior technology consultant for anti-virus software company Sophos.
"The US authorities have demonstrated their determination to deal with virus writers and other cybercriminals. This sends out a strong message to other young people that writing viruses is a fool's game."
The writer of the Blaster-A worm is still at large despite having a £150,000 bounty on their head.