Microsoft Hit by New Wave of Outages

Microsoft Corp. said hacker attacks blocked access to many of its Web sites Thursday, extending a string of costly outages that began late Tuesday with a blunder by one of the company’s own technicians.

The hacker attack Microsoft suffered Thursday temporarily crippled sites including MSN.com and Microsoft.com and was similar to the assault that took down Yahoo.com, EBay.com and other high-traffic sites in February.

Microsoft said that by midday Thursday the sites were fully operational again and that the company had asked the FBI to investigate the attacks.

The company stressed that the attacks were separate from the self-inflicted outages that prevented millions of people from accessing Microsoft sites late Tuesday and much of Wednesday.

But security experts and sources close to Microsoft said those behind the attack were no doubt inspired by the company’s earlier troubles.

“My guess is Microsoft was taking some ridicule for having those problems earlier in the week and somebody decided to take advantage and exacerbate the problem,” said Kevin Poulsen, editorial director of security information company SecurityFocus. “It was probably somebody who thought they’d be cute.”

The continued outages underscored the vulnerability of even the world’s largest software company to the whims of the computer underground.

Experts said that even a year after the high-profile attacks on EBay and Yahoo, there is still little a company can do to prevent such an attack.

Microsoft said the assault appeared to be a so-called denial-of-service attack, meaning hackers bombarded Microsoft with so many phony requests for service that legitimate traffic could not get through. In this case, the assault was aimed at Microsoft routers, devices that direct Internet traffic to the company’s sites.

The afflicted sites were among the most popular on the Web. MSN.com, the company’s portal, attracts more than 10 million visitors a day.

Microsoft was able to deflect the attack by identifying common traits in the packets of data being used to bombard the company and then by filtering packets that carry those traits.

Microsoft shares fell $1.13 to close at $61.81 on Nasdaq.