Microsoft made an official statement on their website, so it is now sure that parts or maybe the whole source code of Windows 2000 and Windows NT 4.0 have been leaked.
On Thursday, Microsoft became aware that portions of the Microsoft Windows 2000 and Windows NT 4.0 source code were illegally made available on the Internet. It’s illegal for third parties to post Microsoft source code, and we take such activity very seriously.
We are currently investigating these postings and are working with the appropriate law-enforcement authorities.
At this point it does not appear that this is the result of any breach of Microsoft’s corporate network or internal security.
At this time there is no known impact on customers. We will continue to monitor the situation.