Apple is adding two-factor authentication to its iOS 9.0 release. The move is part of the company’s overall security improvement in iOS. Apple also is changing the passcode strength from four digits to six, a move that it says ups the number of potential passcodes from 10,000 to one million. The system is more like a two-step verification method than a true 2FA system, as it doesn t require a physical token or biometric identifier, but it adds another roadblock for attackers trying to take over accounts.
Source: https://threatpost.com/apple-moving-to-2fa-six-digit-passcodes-in-ios-9/113270/