The dev-team has cracked the case and found a way to jailbreak Apple’s most recent iOS update, 4.3.1. The team makes it easy to jailbreak the phone with just a few steps. After that you will have more access to your phone and the ability to get unsupported applications among other things. Just remember to restore your device before bringing it to the Apple store or it will void your warranty. If you are an Ultrasn0w user, wait to upgrade since the dev-team still needs to release and update for iOS 4.3.1. This jailbreak supports iPhone 3GS and 4 (GSM only), iPad 1 (notice no iPad 2), and iPod touch 3G and 4G.
2. Download iOS 4.3.1 using the appropriate link (all are official links from Apple):
3. Open redsn0w on your computer
4. Click the “Browse” button and locate the .ipsw file you downloaded in step 2 (pictured below)
5. Hit Next and leave the next page the same, with only the first option checked.
6. Turn off your iPhone and plug it into the computer.
7. Hit next and put your phone into DFU mode using the steps in the app (also pictured below)
8. Some advanced unknown things will pop up on your iPhone screen for a bit, then the iPhone will be jailbroken. Open Cydia and enjoy.