Disclaimer: I take no responsibility for any damage done to your iPhone, all i am doing is helping you out to ease-up your life. Moreover, the applications, software, and sites used in this tutorial are in no way mine, and i don’t take credit for any of them.
Apple released iOS 3.1.3 on Tuesday for all iPhone models and iPod Touches (young children in naughty places) models.
According to apple, iOS 3.1.3 provides security fixes which directly translates into (Breaking unlock and jailbreak for iPhone 3G and 3GS)
As of 8 February 2010 the state of Jailbreak/Unlock is as follows:
iPhone 3GS owners should STAY AWAY from this update. PERIOD (It can be unlocked and jailbroken but requires that you have your SHSH backed-up by Cydia and is a bit messy)
As for you poor-naive-3GSowner fellow whom you upgraded your 3GS into this latest firmware and lost your jailbreak/unlock you can follow this tutorial to get back your jailbreak, but NO UNLOCK FOR YOU YET!!
You should have used cydia to backup your SHSH signatures while you were back on 3.1.2
The goal of this method is to edit your hosts file and redirect itunes to saurik’s servers on which your SHSH signatures are stored.
On MAC you can find your “hosts” file in this location: /etc/
On Windows you can find your “hosts” file in this location: C:\Windows\System32\drivers\etc
All you need to do is open “hosts” in notepad and add the following string “220.127.116.11 gs.apple.com” to the end of your hosts file (without the quotes)
After you have done the previous step, simply put the iPhone into DFU mode and in iTunes Option+Click the Restore button to select the firmware you would like to downgrade to. If you get error message 1011 or 1013 just ignore it, and if you get error message 1015 repeat the entire restore then jailbreak after it fails the second time.
If you encouter “unknown error (3002)”, then you probably do not have your SHSH’s backed-up with Cydia.