Originally Posted by jhawkkw
This I'm not sure about anymore, because if you checkout the International Galaxy S4 Root forum, it appears Samsung pushed out an update that locked the bootloader on carrier/sim free devices. That definitely goes against previous trends for Samsung devices.
is spot on. It is Samsung, in partnership with Centrify, who are rolling out Knox Security and the locked bootloader that it requires, to all the latest Qualcomm devices, S4, S3, Note 2 and already installed on Note 3. Samsung are including this in the firmware prior to passing it on to carriers to add their bloatware, so there is no escaping it.
Currently, any attempt to root or install a custom recovery will trigger the Knox counter, which appears at the top of the screen in download mode, to 0/1 from 0/0. This is a Knox void count. In the absence of any official statement from Samsung it is surmised that this will void your terms of warranty.
Reasons for implementing Knox and further information can be found in the thread over on the S4 forum, Locked bootloader & Knox security on latest firmwares