One of the topics that is requested year after year at our global MVP Summits (event where MVPs from all around the world come to Redmond for a few days) is how do we do security at Microsoft. It should be no surprise that Microsoft has one of the most attacked networks in the world. Well, we don't keep too many secrets about how we do security. Searching our Download Center, you will find numerous white papers on lots of different security topics showing you how we did it. Here are some examples:

Detailed discussion on how Microsoft IT introduced Domain Isolation to the Microsoft global enterprise network.
http://www.microsoft.com/downloads/details.aspx?familyid=a97ddc48-a364-4756-bb3c-91da274118fe&displaylang=en

Overview of why and how Microsoft IT proactively deployed Windows XP Service Pack 2. Windows XP Service Pack 2 is a critical security release that addresses Internet-based security threats.
http://www.microsoft.com/downloads/details.aspx?familyid=36648245-6eac-458e-87bd-046a16f3d385&displaylang=en

Overview discussion on what the Microsoft Corporate Security group does to prevent malicious or unauthorized use of digital assets at Microsoft.
http://www.microsoft.com/downloads/details.aspx?familyid=e959f26c-1f5c-4331-b1fb-6c720795704d&displaylang=en