Over the next few days, Microsoft will begin rolling out an upgrade to accounts including a crucial security feature: two-step verification. The system helps protect your account from hackers by requiring two pieces of information before you can access it — usually your password and something else.
If you have a Microsoft Account, you should definitely turn it on at https://account.live.com/proofs/Manage. Previously, Microsoft had two-step verification for credit card activities at commerce.microsoft.com and xbox.com as well as for accessing your SkyDrive from an unknown computer. Those steps are required for your safety.
If you opt-in to the new security service, you'll be required to submit two pieces of information anywhere you use your Microsoft Account. [Microsoft]