Although by Friday the Sasser worms had dramatically tailed off -- security firm Panda Software reported that Sasser accounted for just 13 percent of all tracked malware Friday, compared with a high of 40 percent on Sunday -- the attacks took their toll in the U.S. and overseas. Delta Airlines, American Express, Associated Press, two major universities, and a leading hospital were among Sasser's victims.
Delta Airlines, for instance, experienced computer difficulties Saturday that forced the cancellation and delay of some flights. The problems began at 2:50 p.m. local time and were fixed by 9:30 Saturday evening, said Katie Connell, a Delta spokeswoman.
Although Connell would not comment on the specific cause of the outage -- "Delta doesn't discuss detailed information about its IT environment," she said -- the airline does use the Windows operating system on some of its servers and desktops. The Sasser worm originally broke onto the Internet late Friday, and by Saturday was wreaking havoc.
American Express was one of the largest U.S.-based firms to report trouble with Sasser. The credit card giant acknowledges Sasser infections on internal desktops starting Sunday, said spokeswoman Judy Tenzer, but the attack didn't have any effect on the company's customer services.