Less than one-fifth of its customers were affected by the clogged traffic for about 90 minutes before the company blunted the attack, he said. A relatively small proportion of users were unable to access Web pages and others, who subscribe to Microsoft's online service, may have been unable to log on, said Microsoft spokesman Tom Pilla. Major sites that fell under attack Tuesday included those of eBay, Amazon, CNN and Buy. While the timing of the attacks remained a mystery, some security experts noted they occurred around a three-day meeting of Internet service providers, in San Jose, Calif., which ended Tuesday. The keynote speech at the North American Network Operator's Group focused on denial of service attacks and was given Monday.
Hackers sometimes seek to garner publicity by timing attacks near symbolically important events.
Federal officials urged businesses to install protective software and take other security precautions. Meanwhile, sensitive government systems were being secured against attacks. First we are taking special action to ensure that all federal systems, including civilian agency systems, and those of the Defense Department, are clean of these infections, which make some systems the unwitting partner in these attacks. But some security experts said the flood of publicity encourage notoriety-hungry pranskters to become more aggressive.