NEW YORK (AP) - The fast-spreading computer virus already blamed for slowing or shutting down e-mail systems worldwide was programmed to coordinate a new type of attack, antivirus experts said Friday.
Instructions written into the latest version of the "Sobig" virus, which began appearing Tuesday, called for infected Windows machines to try to download a program of unknown function as early as 3 p.m. Friday.
"It could be a game, and all these computers would start playing a game, or it could be a destructive program that immediately deletes files," said Mikko Hypponen, manager of antivirus research with F-Secure Corp. in Finland.
Such a program might also attempt to steal passwords or create rogue e-mail servers for spreading junk e-mail, Hypponen said.
He said users should clean their computers using antivirus software - antivirus companies have issued free tools to do so - or turn off machines if they cannot run the disinfecting software.
Users with firewall programs can also block UDP port 8998, which is the Internet opening the virus uses to communicate with the outside world.
The attack was expected to end at 6 p.m., though the virus would try again every Friday and Sunday between 3 p.m. and 6 p.m