Office 365 Multi-Factor Authentication
Multi-factor authentication increases the security of user logins for cloud services above and beyond just a password.
With Multi-Factor Authentication (MFA) for Office 365, users are required to acknowledge a phone call, text message, or an app notification on their smartphone after correctly entering their password. Only after this second authentication factor has been satisfied can a user sign in. If your device is lost, you can disable the password remotely.