KNOX

Samsung Knox provides security features that enable business and personal content to coexist on the same handset. The user can press an icon that switches immediately between Personal and Work mode with no reboot required.
The manufacturer has claimed this feature will be fully compatible with Android and Google and will provide full separation of work and personal data on mobile devices and "addresses all major security gaps in Android."

Samsung Knox devices use an e-fuse to indicate whether or not an "untrusted" (non-Samsung) boot path has ever been run. The e-fuse will be set if the device is booted with a non-Samsung boot loader, kernel, kernel initialization script or data. Rooting the device and installing a non-Samsung Android release will therefore set the e-fuse.
Once the e-fuse is set, a device can no longer create a KNOX Container, or access the data previously stored in an existing KNOX Container.
This information may be used by Samsung to deny warranty service, in the United States, to devices that have been modified in this manner. This is the case even though, in the United States, voiding of consumer warranties in this manner may be prohibited by the Magnuson–Moss Warranty Act of 1975, at least in cases where the phone's problem is not directly caused by rooting. For some devices it is possible to clear the e-fuse by flashing a custom firmware