Sources familiar with the case say that the FBI and Interpol had traced the original upload of the Visual Basic virus, which used encryption techniques to hide itself, to an Excite@Home subscriber account in the Netherlands.

The trace was made within a matter of hours of the investigation starting by the FBI Tuesday.

Investigators had been expecting the virus author to use one of the many anonymous e-mail servers and IP (Internet protocol) data stream rerouters to cover his/her tracks, but they got lucky - the author apparently did not expect to be caught.

The 20-year-old, whose name cannot be given for legal reasons, is from Friesland in the north of the Netherlands and is thought to be a student.

Reports suggest that he turned himself in when he realized the problems his virus was causing, as well as the fact that Dutch police were hot on his trail.

F-Secure, the first IT security company to break the news of the Kournikova virus on Monday, said this afternoon that Atremo AB, its partner in Sweden, was able to assist the FBI in tracking down the location of the Dutch programmer. Atremo's staff handed the details over to the FBI's European staff.

Atremo says that it was able to track down the man using his IP address, which was left in various messages Tuesday in Usenet newsgroups.

Chris Vargas, F-Secure's president, said that server systems around the world were slowed down or similarly impacted as the virus flowed across the Internet.

"As a result of this irresponsible conduct, many e-mail servers were shut down, leading to a decrease in productivity, a slowdown in customer service, and other unknown impacts," he said.

F-Secure says that the escapade appears to have been a misguided attempt to demonstrate that many people have ignored dire warnings of the past and failed to install antivirus software on their PCs.

F-Secure's Web site is at http://www.f-secure.com/ .

Sophos' Web site is at http://www.sophos.com/ .