"He was arrested, but later on released again. He made a statement about his actions, what he had done, how he made the virus and published it on the Internet," said Rambonnet, adding that the man's computer equipment had been confiscated.
"He made a virus to prove how simple it was to make a virus, and how vulnerable computers are for viruses," he added.
Rambonnet would give no further details about the man's identity or occupation, other than to say he is a resident of the town of Sneek.
Meanwhile, in Washington the US Federal Bureau of Investigation (FBI) opened an investigation into the attack, said Debbie Weierman, a spokeswoman for the FBI. The probe involves the collection of information from people who fell victim to the virus. Weierman declined to provide specifics about the investigation and would neither confirm nor deny whether it involved authorities in the Netherlands.
In all likelihood the man who turned himself in to Dutch police is the same person who took responsibility for the virus in a Web posting Tuesday, identifying himself by the user name "OnTheFly," Rambonnet said.
"I didn't do it for fun," the posting said. "I never wanted to harm the people [who] opened the attachment. But after all: it's their own fault they got infected with the AnnaKournikova virus, OnTheFly virus or whatever they call it."
The posting said OnTheFly was prompted to create the virus after reading research by International Data (IDC) suggesting users are ill-prepared for viruses. "I think IDC is right. I also think that you agree with me, according to the rate of spreading," it said.
"I think it's that person passing the blame on to somebody else," said IDC Software Infrastructure Research Director Rob Hailstone. "It isn't right to ask a newspaper not to report a murder because you're worried about copycat murders."
The virus research, which Hailstone presented on IDC's behalf on 5 February, pointed to the risk of a Valentine's Day attack like the infamous "I Love You" virus. Some 37 per cent of users surveyed said they would open an e-mail with a subject line like "I love you" if it came from someone they knew, said Hailstone; another 8 per cent would open it even from someone they'd never heard of.
The "I Love You" virus wreaked havoc on systems worldwide starting last May, causing an estimated $US8.7 billion in damage. A Filipino student was eventually arrested in connection with the bug, but was released because prosecutors lacked a law with which to charge him. E-mail to OnTheFly's address was returned with an error message saying the account had been disabled. The ISP (Internet service provider) @Home Benelux BV, host of the address, is currently investigating whether OnTheFly is indeed one of its users, said spokeswoman Marieke van Kruiningen.
The Visual Basic script (VBS) virus is spread via e-mail carrying an attachment masquerading as a .JPG image of Russian tennis star Anna Kournikova. If activated, it does not destroy or corrupt files, but has clogged e-mail systems by the sheer number of messages it generates in replicating itself. The OnTheFly posting also laid some of the responsibility at the tennis player's feet. "Just because I am a big fan of her. She deserves some attention, doesn't she??" it said, and, "Maybe this is also Anna's blame, she is so pretty."
(Margaret Johnston in Washington contributed to this report.)