Hackers briefly overwhelmed at least three of the 13 computers that help manage global computer traffic Tuesday in one of the most significant attacks against the Internet since 2002. Experts said the unusually powerful attacks lasted for hours but passed largely unnoticed by most computer users, a testament to the resiliency of the Internet. Behind the scenes, computer scientists worldwide raced to cope with enormous volumes of data that threatened to saturate some of the Internet's most vital pipelines. Experts said the hackers appeared to disguise their origin, but vast amounts of rogue data in the attacks were traced to South Korea. The attacks appeared to target UltraDNS, the company that operates servers managing traffic for Web sites ending in "org" and some other suffixes, experts said. Company officials did not immediately return telephone calls from The Associated Press.