Greenpois0n released by Chronic Dev team, uses the same bootrom exploit used by Limera1n. Greenpois0n can jailbreak 3GS on iOS 4.1. You can easily jailbreak your iDevice by following simple steps:
Step1: Download Greenpois0n.
Step2: Run Greenpois0n and click on “Prepare to Jailbreak (DFU)” button.
Step3: Power off your by pressing sleep button and connect iDevice to PC.
Step4: Now run Greenpois0n and click on “Prepare to Jailbreak (DFU)” button and simply follow on-screen instructions.
Step5: If your iDevice is not in DFU mode then restart it again and follow all the steps again (Step1 to Step4).
Step6: After clicking on “Jailbreak” option, Greenpois0n will automatically jailbreak your iDevice and it restart automatically.
That’s it. This will simply jailbreak your iPhone/iPod Touch on iOS 4.1.
Limera1n and Greenpois0n works with windows only and their MAC version is under development.