Jailbreak iPhone 3.1.2 OS with Blackrain
Warning: The current update of Blackra1n only supports iPhone OS 3.1.2, do NOT use this tool if you are using an earlier version of iPhone OS. We have unconfirmed reports that BlackRa1n supports iPhone OS 3.1 as well, but we are not sure.
Also, do not upgrade to 3.1.2 using iTunes if you want to keep your unlock. Baseband cannot be downgraded.
Download Blackra1n for iPhone/iPod Touch
You can download BlackRa1n to jailbreak iPhone and iPod Touch OS 3.1.2: Download blackra1n Once downloaded, make sure to update your iTunes to the latest version. Update: Jailbreak iPhone 3g/3GS with iPhone OS 3.1.3 with Sn0wbreeze