Apple rolls out two-factor authentication to its iCloud and Apple ID accounts. Users will be required to enter a four-digit code they may receive via SMS message. Apple will be using both the app and SMS versions, providing security codes through texts as well as the FindMyiPhone app. The option will be initially available in the United States, United Kingdom, Australia, Ireland, and New Zealand. Users who activate the option will have the ability to generate a new recovery key from the My Apple ID website.
Source: https://thehackernews.com/2013/03/apple-adds-two-factor-authentication-to.html