Microsoft has made a big deal out of asserting that Linux is not fit for the enterprise. But Microsoft itself is using Linux to help protect its servers against denial-of-service attacks.

According to a post on the Netcraft Web site, Microsoft changed its DNS settings on Friday so that requests for www.microsoft.com no longer resolve to machines on Microsoft's own network, but instead are handled by the Akamai caching system, which runs Linux.

Akamai runs a service to help boost Web site performance by caching copies of Web sites on many servers in many locations. Akamai can help defend against denial-of-service attacks by spreading the attack among many servers. Just as a distributed denial-of-service attack enlists large numbers of systems to attack a single server, Akamai presents a distributed defense against denial-of-service attacks.

As of this writing, Netcraft reports that www.microsoft.com is still running on Linux, although microsoft.com is reported as running on Windows Server 2003.

A Microsoft spokeswoman said the company "respects the fact that [its partners and vendors] may have diversified business models and operate in mixed IT environments. Microsoft's main concern is doing whatever it takes to help ensure customers can get to the Blaster worm patch to protect their computers.... Microsoft is using Akamai's extensive worldwide network to distrubte the massive traffic that is illegally being directed at Microsoft by hackers."

The Blaster worm, which struck the Internet last week, was set with a payload designed to trigger this past Saturday and flood the address windowsupdate.com with a massive denial-of-service attack. But windowsupdate.com never was a Microsoft site, it was an incorrect address for picking up Windows updates. Until Saturday, Microsoft had set windowsupdate.com to redirect to windowsupdate.microsoft.com; Microsoft protected itself last week by switching off that redirection.

An Akamai spokeswoman declined to comment, except to confirm that Microsoft is a customer.

Microsoft using a Linux service is ironic, given that Microsoft has identified Linux as its biggest competitor. In a conference call with analysts last month, company CFO John Connors ranked Linux as the #2 risk faced by the company. The #1 risk was the general economic environment, Connors said. Nearly one in five small and mid-sized businesses are using Linux on the desktop.

In tomorrow's news: McDonald's executive found eating at Burger King.