WASHINGTON - A new variety of unusually powerful Internet attacks can overwhelm popular Web sites and disrupt e-mails by exploiting the computers that help manage global Internet traffic, according to security researchers. First detected late last year, the new attacks direct such massive amounts of spurious data against victim computers that even flagship technology companies could not cope. In one of the early cases examined, the unknown assailant apparently seized control of an Internet name server in South Africa and deliberately corrupted its contents. Name servers are specialized computers that help direct Internet traffic to its destinations. The attacker then...