Over the next couple days we will roll out a major upgrade to Microsoft account, including optional two-step verification to help keep your account more secure.
Microsoft has increasingly focused on delivering connected devices and services that are currently used by more than 700 million people around the world. A Microsoft account is the key that unlocks your experience across these products—from your Windows PC to your Windows Phone, from Xbox to Outlook.com, from SkyDrive and Skype to Office and much more.
For the complete post and more information on this subject, see http://blogs.technet.com/b/microsoft_blog/archive/2013/04/17/microsoft-account-gets-more-secure.aspx.