There’s a bit difference between rooting International Galaxy S3 and the AT&T Galaxy S3, so here’s a separate rooting guide for you. The guide covers all the steps involved in rooting AT&T Samsung Galaxy S3, follow each step carefully and you will end up with root access on your smartphone. Here you go:
I. Before You Begin:
1. You must have ADB installed on your PC. You can see our guide on how to install ADB.
1. The warranty of your smartphone will be voided once you root it. However, you can regain the warranty by either applying stock firmware or unrooting your phone.
2. Make sure your phone is charged fully. It is to avoid any interruptions during the process.
II. Downloading Required Files:
1. Download the Stock Odin Tar from here. (Download link is there in the first post with the title ATT Image)
2. Download the Odin Tool from here. (It’s attached there in the thread)
3. Download the ClockworkMod Recovery from here.
III. Rooting AT&T Samsung Galaxy S3:
1. Place all the downloaded files on the Desktop of your PC.
2. Extract files from the Odin and Stock Odin Tar archive to your Desktop.
3. Double-click the Odin executable file to launch it.
4. Turn OFF your smartphone using the Power key.
5. Reboot your phone into the download mode so it can work with Odin. To do so, press and hold Volume DOWN+Home+Power keys together.
6. While your phone is in download mode, connect it to your PC using the USB cable.
7. From the Odin tool, choose PDA tab and then select the stock_root67.tar file you extracted earlier from the archive.
8. Make sure that Auto Reboot and F. Reset Time options are checked in the Odin, leave others unchecked.
9. Click on the Start button to commence the flashing process.
Your phone should now be rooted and from now on, you can install root-only apps on it. Now, move on to the following procedure to install ClockworkMod Recovery on your smartphone.
IV. Installing ClockworkMod Recovery on AT&T Galaxy S3:
1. Extract the recovery.img file from the ClockworkMod Recovery file to your Desktop.
2. Connect your phone to your PC using the USB cable.
3. Transfer the recovery.img file to the root folder of your phone’s SD card.
4. Open a Command Prompt window where you have installed ADB and type in the following commands:
dd if=/sdcard/recovery.img of=/dev/block/mmcblk0p18
5. Now reboot your smartphone by issuing the following command:
Congrats ! You have successfully installed ClockworkMod Recovery on your AT&T Samsung Galaxy S3 smartphone. Now you can taste out the custom ROMs on your phone.
If this procedure helped you, then please head to the official thread over at XDA Forum to thank/donate to the original developer of this root and recovery method !