Two men, one in Morocco and one in Turkey, have been arrested over the unleashing of a computer worm that affected US firms earlier this month.
Aircraft maker Boeing was hit by the Windows 2000 bug
Moroccan authorities detained Farid Essebar, 18, while Atilla Ekici, 21, was arrested by Turkish authorities on Thursday, the FBI said.
They are believed to be responsible for the Zotob worm that targeted computers using Microsoft Corp operating systems.
More than 100 firms were affected including CNN and The New York Times.
FBI Cyber Division Assistant Director Louis Reigel said there had been close teamwork between the FBI, Microsoft Corp and the Moroccan and Turkish authorities.
"This case happened very quickly," he told Reuters news agency. "Had we not had those entities involved in this investigation, I suspect it would still be ongoing today."
He said the two men would face prosecution in their native countries with FBI officials providing evidence.
The Zotob worm emerged just a week after Microsoft Corp warned of a security flaw in the Plug and Play feature of Windows 2000.
It caused computer outages at several large US news organisations as well as to heavy-equipment maker Caterpillar Inc and aircraft-maker Boeing.
Microsoft general counsel Brad Smith said many consumers had kept their software up-to-date so the impact of the worm was limited.
The computer giant's team of 50 investigators had analysed the Zotob worm and its variants to discover where it was coming from, he said.
The software industry was working hard to improve computer security and had made significant gains in a short time, he said.
"The fact that we were able to see these arrests in less than two weeks and see them halfway around the world really drives that point home," he said.