How to jailbreak iphone4 using greenpois0n

How to Use Greenpois0n

To get started using this jailbreak, the following are the recommended procedures. A word of warning: some of the first to attempt this jailbreak are reporting issues and some are even saying that the jailbreak doesn't work. For others, it's taking a few times before the process works as designed. Others still say they don't have any issues at all. In other words, proceed at your own risk!

If you're feeling daring, then do the following:

1. Backup your device and restore it to iOS version 4.2.1, setting it up as a new device within iTunes.
2. Plug in your device to your computer and turn the device off.
3. Download and run greenpois0n on your computer. The onscreen instructions will guide you as to how to get into DFU mode on the device, which involves a series of button presses (press and hold sleep, press home, release sleep, continue holding home).
   
4. When your phone or other device enters into DFU mode, the jailbreaking process will begin.
5. When the process completes, you'll have a new "Loader" icon on your homescreen. (Apple TV jailbreakers, of course, will not. They will need to use Terminal and SSH instead).
   
6. Tap the icon to install Cydia, the jailbreak app store.