The Samsung Galaxy S3 is an older device now which makes it the perfect secondary handset to keep in your room and use it to flash custom ROMs and custom firmware that becomes available. Before you can tinker with the operating system, you must first open the ports with root access by following the guide below.
- You can use this guide if you are running the official Android 4.0.4 ICS software update. Head to the Settings, followed by the About Device menu to check that.
- You must stay at the About Device menu and check your model number is SGH-I747. There are several different variants of this handset, and you can only flash the files below for the I747.
BEFORE WE BEGIN
- Download the Samsung USB Drivers  for mobile phones from our link.
- Take the time to back up your current ROM by navigating to the backup option from the Settings, or by downloading an app from Google Play such as Helium.
- You are immediately voiding the warranty by following the guide.
HOW TO ROOT THE SAMSUNG GALAXY S3 SGH-I747 IN ANDROID 4.0.4 ICE CREAM SANDWICH
- Download the rooting file to your computer from here .
- Download Odin from here .
- Extract both files to the desktop.
- Open the Odin tool.
- Completely turn off the smartphone by holding down the power button for 15 seconds and releasing it.
- Reboot the phone to Download Mode .
- Press the Volume Up key at the yellow warning triangle.
- Connect the S3 to the computer with the USB cable.
- Click the PDA button in Odin and upload the CF-root.tar file from the other extracted file on the desktop.
- Click the Start button and wait for the flashing to stop.
Download the BusyBox  app as your first application that’s only available for a rooted Android if you like.