The attack started early Tuesday morning in the US when Microsoft employees noticed massive spikes in traffic, said Adam Sohn, a spokesman for the Redmond, Wash.-based software company. Microsoft's Web site didn't shut down, but it did endure a 3% to 7% degradation in performance, Sohn said.
As a result, users weren't able to view pages immediately.
The attack against Microsoft came in the form of a "synflood," a type of denial-of-service attack that prevents PCs and Web servers from communicating. When this type of attack occurs, the server continues to send out new requests to identify the visiting computer without making a connection.
When the synflood began, Microsoft employees shut off access to the Web site once they determined which IP address the attack had come from, Sohn said. Another reason Microsoft's site was able to stay up is that it utilizes vast amounts of server capacity.
The one positive aspect of the attempted attack: Windows 2000 lived up to its expectations, Sohn said. "It was a great battle test for Windows 2000 - they came at us hard," but the security settings in the server level kept out the synflooding, he said.
Microsoft later reported the attack to law enforcement officials, said Sohn. He didn't specify which agencies the company notified. The only information that is known is where the attack physically came from, he added.
The company plans to step up its security efforts, said Sohn.
"Often Microsoft is a target because we're very visible, and we tend to be vigilant" in security efforts, Sohn said. Attempts are made every day to access corporate information on the the company's network and the site. Recent denial-of-service attacks on such sites as CNN and Yahoo heightened Microsoft's security, he said.