The impact from the attacks appeared limited, and there were no reports of outages or even delayed e-mails.

A flood of data, spiking nearly 700 percent more than usual traffic, was aimed at Internet providers and Web sites on the East coast starting about 2 a.m. EDT, then shifted toward providers and sites on the West coast, said a U.S. official, speaking on condition of anonymity.

But unlike some recent so-called "denial-of-service" attacks, which employed hundreds or thousands of computers to overwhelm Web sites, this latest attack appeared to be coming from a relatively small number of machines, the official said. That has allowed Internet providers to protect their networks more easily by filtering data from the attacking computers.

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