The fast-spreading Sobig.F e-mail virus has slowed markedly and failed for a second time to launch a remote data attack using thousands of infected personal computers.
Sobig.F, which first emerged on August 18th, was programmed by an unknown creator to unleash a data attack yesterday.
But with the trigger - a computer program unwittingly installed on 20 poorly defended computers, mostly in the United States and Canada - deactivated on Friday, yesterday's attempt was a non-event, according to reports from technology security company Symantec.
An initial automated barrage planned for Friday was averted after US government and security industry experts raced to diffuse the digital trigger that could have taken control of more than 100,000 infected computers and possibly crippled the Internet.
The number of infected computers worldwide fell dramatically from Saturday to Sunday, declining by one-third in the 24-hour period to 98,205 from 145,264, according to a virus map from anti-virus software maker Trend Micro.
North America had the highest number of infected computers at 68,911, a one-day drop of 22 per cent. The number of infected computers in Europe fell by 51 per cent to 26,727 machines. But from a smaller base, infections in Asia jumped 41 per cent to 8,258, according to Tokyo-based Trend Micro's Web site.
SoBig.F is the sixth version of a virus that first appeared in January. Each one has been stronger than the previous, security officials said. SoBig.F is programmed to expire on September 10th.