Microsoft’s main web site at www.microsoft.com experienced performance problems this morning, probably due to a DDoS attack launched by a new version of the MyDoom virus.

A dynamically updating graph is available here, with performance data for all the sites involved in the MyDoom DDoS located here.

This morning at around 9am GMT response times to www.microsoft.com surged, and for a time the site failed to respond. Subsequently, the www.microsoft.com began dropping requests without User-Agent headers, apparently to differentiate between traffic from Web browsers and the DDoS attack agents. Our monitoring requests, which do not normally set a User-Agent, were also dropped. These were changed to supply a user-agent header on requests to www.microsoft.com around 2pm GMT and have since seen mixed results, with relatively normal results from London, but some extended and erratic response times from Atlanta, New York and Texas.

General internet connectivity has not been noticeably impaired with 41 of 52 leading hosting company sites experiencing no failed requests in the last 24 hours.