As Cyrus Farivar noted on Ars Technica recently:
As part of its iOS 9 announcement on Monday, Apple revealed that all newer iDevices equipped with TouchID and running the newer version of the operating system will be required to upgrade from a four-digit to a six-digit passcode. Passcodes remain optional, and users can create a more complex alphanumeric password, but six digits will be the minimum. After 10 failed attempts to type in the code, the device will erase itself.
According to Apple (and math), this will vastly expand the effort required to crack a four-digit passcode. Instead of 10,000 possible combinations, newer iOS devices will soon have one million. This change affects the iPhone 5S, 6, 6 Plus, iPad Air 2, and iPad Mini 3.…
For all of the gory details, including touching on the politics, PYBT: Apple to require 6-digit passcodes on newer iPhones, iPads under iOS 9
