MSDN: One of the things we talk quite a bit about with Windows 8 is making sure Windows is a safe, secure, and reliable computing environment. We have always provided a broad range of solutions for achieving these goals and work closely with a broad range of industry partners. We continue to enhance these capabilities with Windows 8 while making sure you always have choice and control over how to protect and manage your PC. With Windows 8 we are extending the protections provided by Defender to address a broader range of potential threats. Jason Garms, the group program manager of our reliability and security team authored this post that represents work across several teams. –Steven
Read the story here: http://blogs.msdn.com/b/b8/archive/2011/09/15/protecting-you-from-malware.aspx