We will now look at the different methods available to root an Android device. The primary factor that influences your choice of method is whether the underlying boot loader is locked or unlocked. Gaining root access on a device with an unlocked boot loader is very easy, while gaining root access to a device with a locked boot loader is not so straightforward, which means that unlocking your Android phone’s bootloader is often the first step to rooting and flashing custom ROMs. This can be done either through fastboot mode (discussed in earlier sections) or by following a vendor-specific boot loader unlock procedure. Once the device bootloader is unlocked, the next step is to copy the su binary and grant it executable permissions. This can be done in many ways. 

The following is how to root a Samsung Galaxy S7 (International SM-G930F/FD/X, Korean SM-G930K/L/S, and Canadian SM-G930W8 Exynos models):

1. Make sure OEM unlock is enabled in the Developer options.
2. Download ODIN (available at https://build.nethunter.com/samsung-tools/Odin_3.12.3.zip) and extract the contents of the archive to the directory of your choice.
3. Download the TWRP image (available at https://twrp.me/samsung/samsunggalaxys7.html).
4. Reboot your device into download mode. To do this, hold the Volume down + Home buttons while your device reboots. Once you see the download mode warning screen, press Volume up to continue.
   Start Odin and put the TWRP image in the AP slot; don't forget to disable Auto-Reboot. Start flashing the recovery.
5. To exit download mode, hold Volume down + Home + Power; when the screen blanks, immediately change Volume down to Volume up.
6. Allow system modifications by swiping right.
7. Download SuperSU (available at https://download.chainfire.eu/supersu).
8. Transfer the archive with SuperSU to the device via MTP and install it via the corresponding TWRP option.

Rooting is a highly device-specific process and hence the forensic investigator needs to be cautious before applying these techniques on any Android device. Rooting a device has both advantages and disadvantages associated with it. The following are the advantages of rooting: 

• Rooting allows modification of the software on the device to the deepest level—for example, you can overclock or underclock the device's CPU.

• It allows restrictions imposed on the device by carriers, manufacturers, and so on, to be bypassed.
• For extreme customization, new customized ROMs can be downloaded and installed.

The following are the disadvantages of rooting:

• Rooting a device must be done with extreme care as errors may result in irreparable damage to the software on the phone, turning the device into a useless brick.
• Rooting might void the warranty of a device.
• Rooting results in increased exposure to malware and other attacks. Malware with access to the entire Android system can create havoc.

Once the device is rooted, applications such as the Superuser app are available to provide and deny root privileges. This app helps you to grant and manage superuser rights on the device, as shown in the following screenshot:

We will now look at root access.