Greenpois0n is a tool developed by the Chronic Dev Team. It is necessary for those who want to take advantage and benefit from jailbreak without unlocking their iPhone, or for those that already have a factory unlocked phone. It is also good for the iPad users that wanted to pass to iOS 4.2.1, but were disturbed by the lack of a jailbreak that doesn't require to be connected to a computer everytime you restart your device.
Chronic Dev Team decided to make the release before the advent of iOS 4.3 because Apple has already managed to parry the hackers blow even from the beta versions of future firmware. You should remember that if you decide to jailbreak, you can only rely on the current Greenpois0n version if you have iOS 4.2.1 and not iOS 4.3. Many thought at the Chronic Dev Team would skip 4.2.1 and wait to release the Untethered JailBreak for 4.3. Apparently they like the challenge and will allow Apple to fix this exploit and dig for a new exploit for the next version when it is released officially. iOS 4.3 is currently available only to developers.
There is now a working Untethered Jailbreak solution for iOS 4.2.1 for both Mac and Windows users. Prior to this week, only Mac users could use the Greenpois0n app to Jailbreak the latest release of Apple's iOS 4.2.1.
Many of us have resisted upgrading to iOS 4.2.1 because we would lose many benefits of JailBreaking. We were not willing to use a Tethered solution that had existed for several months. With a Tethered Jailbreak, the iDevice would have to be physically connected to a desktop to re-JailBreak after a reboot of the device. Untethered devices can reboot freely without worry.
There is no need for tutorials, all you have to do is follow a few simple steps: Sync your device to your computer to have a latest backup, Download Greenpois0n, connect your device to your computer, press "Jailbreak" on the Greenpoi0n app, and following a series of button holds and releases.
I will update this post after I perform this to my iPad.
Disclaimer: JailBreaking is not illegal; however, Apple does not like or approve it. They will not service a device that is in a JailBroken state. The JailBroken state can be undone at anytime my doing a restore from iTunes on the desktop. Do not attempt until you fully understand the process and possible hiccups. Use Google and Youtube to learn more about JailBreaking 4.2.1.
Related: After you JailBreak your iPad. be sure to check out my best Cydia apps for the iPad.
Update: I performed the GreenPois0n JailBreak on Super Bowl Sunday to my iPad. My iPad was at iOS version 3.2.1 and it was JailBroken previously with Limera1n. I used the AptBackup app first to backup the list of Cydia apps that I had loaded.
I sync'd my iPad to my Windows laptop to backup the iPad content and to perform the iOS update to 4.2.1. After the backup and iOS upgrade, I downloaded the Greenpois0n software for Windows and launched it. I performed the