[单项选择]The "MyDoom" virus could presage a generation of computer attacks by organised gangs aiming to extract ransoms from online businesses, experts said yesterday. The warning came as the website run by SCO, a company that sells Unix computer software, in effect disappeared from the web under a blizzard of automated attacks from PCs infected by the virus, which first appeared a week ago. The "MyDoom-A" version of the virus is reckoned to be the worst to have hit the internet, in terms of the speed of its spread, with millions of PCs worldwide believed to be infected. Such "zombie" machines begin to send out hundreds of copies of the virus every hour to almost any e-mail address in their files. On Sunday they began sending automated queries to SCO’s website, an attack that will continue until 12 February. The attack is the web equivalent of ringing the company’s doorbell and running away a million times a second, leaving its computers unable to deal with standard requests to v A. an organization of gangs B. the infection of PCs C. the sale of a software D. a website’s vanishing