Its now been a number of years since iPhone Dev Team unleashed this amazing tool and to say how important the role of ultrasn0w has been to many iPhone users would be an understatement. Anyone who relies on their carrier / network to be unlocked in order to use their iPhone 3G, 3GS and iPhone 4 on another GSM carrier, now has the opportunity to take the iOS 4.3.1 upgrade while remaining unlocked thanks to ultrasn0w 1.2.1.

The iPhone Dev Team have worked their magic to make ultrasn0w functional once again for the iPhone 4 (GSM), 3GS and 3G. They've also added a little extra to correct a signal bar issue for anyone maintaining an older baseband but not using an unlock.

Its important to stress that this tool will not unlock newer basebands but its ability to function still requires that your iOS device retains the older baseband. Therefore if you're intending to upgrade to iOS 4.3.1 but want to continue using alternative carriers / networks, make sure you use iPhone Dev Team's Pwnage Tool to maintain your existing baseband. Attempting to upgrade straight off iTunes in the hope of using redsn0w to jailbreak will definitely result in a baseband upgrade and therefore ultrasn0w being locked out.

Once you've jailbroken your iPhone using Pwnage Tool, tap on Cydia and search for ultrasn0w to get your iPhone unlocked to any carrier of your choice, then just reboot your phone. Ultrasn0w is not an application that requires downloading to your computer.

[via iPhone Dev]