SAN JOSE, Calif. -- Several major Web sites - including Yahoo!, Microsoft and Google - were inaccessible at times early Tuesday due to what the company that distributes them online called an attack.
The problem began about 9 a.m. EDT and lasted less than two hours, said Jeff Young, a spokesman for Akamai Technologies Inc., whose network of servers mirror some of the Web's top destinations to improve their performance.
Young called it a "large scale, international attack on Internet infrastructure." However, there was no evidence that non-Akamai infrastructure was affected.
Amit Yoran, head of the Department of Homeland Security's cybersecurity division, declined to comment on the alleged attack and its scope, deferring questions to Akamai. The government-funded CERT network emergency response team did not immediately return a call seeking comment.
Keynote Systems Inc., a Web performance measurement service, said the only sites where it saw trouble Tuesday were those served by Akamai.
Young said he had no immediate information on the nature of the alleged attack, nor did he know where it originated or other Internet infrastructure companies that might have been targeted.
Keynote said the availability of the top 40 sites it monitors dropped from 100 percent to just over 80 percent during the outage.
"We discovered it wasn't the Internet as a whole but a few large sites that dropped to nearly zero," said Lloyd Taylor, Keynote's vice president of technology and operations.
Major Web sites hire Akamai to distribute their content on its servers around the world - which helps balance demand, improve reliability and speed up delivery.
Taylor said the outage was consistent with a technical failure or an attack on Akamai's domain name server system, which routes traffic by translating Internet text addresses to the numerical addresses of actual computers.
During Tuesday's incident, Akamai's systems were slow in this regard, Young said. Users either experienced sluggish performance or time-out errors.
The company claims to have the world's largest distributed content network, consisting of more than 15,000 servers in more than 60 countries. At peak times, it can handle as much as 15 percent of the Internet's traffic, Young said.
The Akamai network experienced another technical problem in May - an issue Akamai said was software-related.
Shares of Akamai were up 71 cents, to $15.62, in Tuesday trading on the Nasdaq Stock Market.