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Last year, Jan de Wit was sentenced to 150 hours of community service for creating and sending out the e-mail worm. The appeals court confirmed the sentence.
"I had hoped he would be found not guilty," said Theo Jansen, De Wit's lawyer. "My client never intended to do any damage and no damage was ever proven."
No damage claims were filed with the prosecutor's office, but the US Federal Bureau of Investigation (FBI) named 55 victims of the Kournikova worm who suffered total damage of $166,827 (£107,340).
De Wit used a worm-making toolkit to create a worm that, under the guise of an e-mail image of Russian tennis star Anna Kournikova, spread like wildfire for two days in February 2001.
At his initial trial, De Wit stated that he did not know what he was doing or what the consequences of posting the virus in an Internet newsgroup could be. The judges did not believe him because De Wit had a collection of about 7,200 computer viruses and worked in a computer store.
De Wit was charged with spreading data via a computer network with the intent to cause damage, a crime punishable by four years in prison and a maximum fine of about €45,000 (£29,000). The prosecutor, however, only asked the court for a sentence of 240 hours of community service.