Big new greenpois0n update, which will allow us to apply an untethered
jailbreak to our iOS devices running iOS 4.2.1 ( and iOS 4.1.1 ).

1. Download greenpois0n

2.Restore your iOS device to iOS 4.2.1. Note: if you need to unlock do not
do this. Restoring to a stock FW will upgrade your baseband and you
will loose the ability to unlock. *

3. Connect your iPhone and load greenpois0n

4.Click Jailbreak and follow the instructions on the screen to put your iOS in recovery mode.

 5.Once in recovery mode, automated process will start and will jailbreak your device.

6.After the jailbreak is done, you will have a new application on your springboard called Loader. Use it to install Cydia