A domain name outage Tuesday morning left many popular Web sites such as Yahoo, Google, Microsoft.com and Apple.com temporarily inaccessible, according to a Web research company.
For just more than two hours--from 5:30 a.m. to 7:45 a.m. PDT--many of the world's most popular sites suffered from widespread outages, according to Keynote Systems, which compiles statistics related to Web surfing. On a typical day, the top 40 sites measured by Keynote rarely dip below 99 percent availability. On Tuesday, however, Keynote saw availability drop to 81 percent.
Keynote said the site blackouts stemmed from an outage suffered by Akamai Technologies' domain name server system, which translates word-based URLs into numeric Web addresses to link surfers to company sites.
Though Keynote did not have solid confirmation of the source of the issue, one executive there speculated that Akamai may have suffered a denial-of-service attack. DoS attacks flood a company's servers with millions of simultaneous requests for data. The attacks often overwhelm and shut down servers.
"I know folks who built Akamai's infrastructure, and they are really sharp people," Lloyd Taylor, vice president of technology at Keynote, said in an interview. "While it's possible that there was internal failure, I think it's a low possibility."
An Akamai representative did not return calls requesting comment.
With the sites back up, it appears the DNS issue has been resolved, but Yahoo's new Web-based e-mail service, launched Tuesday, continues to have problems.
Since early Tuesday morning, users have experienced glitches with Yahoo Mail, such as site inaccessibility, slow page loads and inoperable buttons on the site. A Yahoo spokeswoman said the company is "investigating the potential impact of a widespread DNS issue on our services." But launch-related bugs are also a possibility.
"As we upgrade tens of millions of Yahoo Mail accounts for consumers worldwide, some users may experience temporary fluctuations in the service as we update our systems," said Yahoo spokeswoman Mary Osako. "We expect Yahoo Mail accounts to resume to normal after the upgrades are completed."