A few days back, Dev-Team released the PwnageTool 3.1.4 to jailbreak iPhone 2G/3G/3GS and iPod Touch 1G/2G 3.1.2 Firmware. So, in order to unlock your iPhone 3G/3GS with Ultrasn0w, you should first jailbreak your iPhone 3G/3GS with 3.1.2 firmware. If you’re done with that, then follow the guide given below.

1. After successfully jailbreaking your iPhone, go to Cydia and select Manage tab.

2. Choose Sources, tap on Edit and then on Add and type the given URL in the box and add it.

http://repo666.ultrasn0w.com/

3. Now open Ultrasn0w app(or search for Ultrasn0w) and install it on your iPhone.

4. After the installation is complete, it will automatically unlock your iPhone 3G/3GS with 3.1.2 Firmware.