Update: Dev-Team has released an untethered jailbreak!
With this custom firmware and the included files, you can use iTunes to jailbreak your iPhone. Then use the included tetheredboot utility to boot tethered, as this is a tethered jailbreak, meaning you will need to connect the iPhone to your computer after a reboot. It’s quite simple though, and works fine until a true untethered jailbreak is released. This guide uses Mac OS X.
This bundle includes all files you need.
First put your iPhone in DFU mode. Hold the power and home button for 10 seconds. Then release the power button while still holding the home button. iTunes will pop up with a message saying it has detected an iPhone in Recovery mode and the screen will remain black on the phone. If this doesn’t happen try again, making sure your timing is OK.
Now in iTunes, select the downloaded custom ipsw (iPhone3,1_4.3.1_8G4_Custom_Restore.ipsw) by option-clicking the Restore button. Once that’s finished restoring you will need to use the tetheredboot utility to boot.
Put your iPhone in DFU mode again.
Open the Terminal application, located in /Utilities. Drag the tetheredboot app to the terminal window. Now enter the following exactly:
-i [drag included ibss file] -k [drag included kernelcache file]
Now hit enter and let tetheredboot do it’s thing. Ignore any libusb error output you see. When it’s done the screen on the phone will turn white and it will boot up in a jailbroken state. Sometimes this takes arouned 60 seconds or more, so be patient when the screen is white.
That’s it, your iPhone 4 is now jailbroken running the latest 4.3.1 iOS.
Note: This will erase all info on the iPhone, so be sure to make a backup in iTunes prior to following this procedure.
If anyone would like me to make a version of this for the iTouch or other iPhone model, let me know. But if you’d like to do it yourself, check out Redmond Pie’s article detailing the creation of custom firmware files.