It seems that with the arrival of the latest Jellybean firmwares for Samsung Galaxy S III, Samsung has also introduced a new bootloader that checks to see if the phone / system has been modified / rooted, if that is the case, every time you reboot your phone you'll notice a Red ! Exclamation mark in the upper left corner of your screen and the counter for the custom firmware will increase with +1 also.
This is not an concerning issue fol daily use, but if your phone still has warranty and you want to be prepared for sending it to repairs, you'll need to flash the Old Bootloader from ICS that will allow you to remove the Red ! Exclamation mark and reset the custom firmware counter back to zero with the help of the triangle /Away app.
For this operation to succeed, you will need the following:
Samsung USB Drivers v18.104.22.168: here (credits to SamHaLeKe)
Odin3 v3.07: here
Old Bootloader file: here
Follow these steps properly:
1. Boot your phone into Download Mode by simultaneously pressing the power button, home button and volume down key. Now you will see download mode and you will be asked if you want to cancel or continue. Press volume up to continue.
2. Open Odin on your PC and use the data cable to connect your phone, you should see a "Added" message that appears in the left text box.
3. Select the Old Bootloader file by pressing the PDA button (NOT Bootloader!) and navigating to its location.
4. Very Important = Be sure that the you don't touch anything else in Odin, just Auto Reboot and F.Reset Time should be checked by default, otherwise you check the corresponding boxes and leave everything else untouched!
5. Hit Start, it should take about 10 seconds, after that the phone will reboot and you can disconnect it, that's all, now you can use the Triangle Away app to reset your counter and remove the !.
Bonus: Get Triangle Away from here. The first time you use it, press "Reset flash counter" (it will not reset reset your counter automatically, you still have time to think), the phone will reboot into a special boot kernel mode and you will see some info on the screens, just follow those instructions to complete the process.
It seems that in the latest LLA build the old bootloader method doesn't work anymore!
will update this post with new info asap...
It seems like the guys were hard at work and the finally got a new way to revert back to old ICS bootloader and this one is much simpler than the method above, BUT it only works if you already flashed the new XXELLA firmware that contains the new shitty locked bootloader! Don't try to flash this on top of previous firmware version, risk of bricking the device is very high!
So, here we go:
1. Download the ICS bootloader from here - mirror
2. Reboot into Recovery Mode by simultaneously pressing the power button, home button and volume up key.
3. Select the path of the ICS bootloader and flash it.
4. Reboot phone / done!
Now use Triangle Away to get rid of the fuckin' red ! exclamation sign and set counter to 0.
Be aware that if you continue to use a custom kernel / recovery, your counter will be set to 1 right after you reset it to 0 via Triangle Away, to permanently reset counter to 0 and keep the Official status, you need to flash a stock firmware!
More details on this method and how to keep counter to 0 can be found @xda.