Days before the author of the most prolific computer virus in history receives his likely US jail sentence, evidence has emerged that virus writers worldwide are beginning to cover their tracks, according to one expert. Graham Cluley of Sophos Anti-Virus says many sites frequented by virus writers have been shutting down in the wake of the Melissa Virus trial, including Japanese Web site Sok4ever.com, which vanished just days ago. Melissa author, David L Smith, is to be sentenced on Friday. Sok4ever.com, which hosted the Web sites of a number of different virus writers, vanished over the weekend, says Cluley, who spoke to journalists earlier this week. He describes this as particularly timely, given Smith's situation: "This Japanese Web site was being used by a lot of virus authors to spread their wares." Another high-profile virus site to go offline recently is Source of Kaos. Cluley doesn't expect that the danger from computer viruses will go down significantly, however: "In the short term, virus distribution is going to go down. In the long term, it's hard to say. Some may scurry away into a corner and disappear, others may appear elsewhere. It's a bit like pulling weeds out of a garden." The first ever computer virus to remotely update its definitions, Babylonia.exe, was linked to the Sok4Ever site, according to Cluley. The Melissa virus wreaked unprecedented havoc to computer systems worldwide when unleashed in March last year. It was the first strain of computer virus to make use of email spreading itself among users of Outlook Express at a extraordinary rate. David L Smith was arrested the following month, and later admitted causing approximately $80m (£50m) of damage to businesses worldwide. It is widely expected that he will receive a prison term when sentenced this Friday. What do you think? Tell the Mailroom. And read what others have said. Take me to the Melissa Virus Special.