It's just few hours after iOS 4.3.4 got to the markets that PwnageTool 4.3.3 bundle was reported to unlock it. Jailbreaking is a hacking method that gives you access to the root file system, after which you can install any third-party software on your device. Jailbreaking is not illegal, but the Apple people might not consider your warranty any longer. However, you can reverse the modifications you made by restoring OS through iTunes and they might never know about it. Apart from the iPad2, the jailbreak is reported to work on iPhone, iPad and the iPod touch. The PwnageTool has been a major tool in jailbreaking the latest operating systems of Apple's mobile devices. Its main advantage is that it preserves the baseband even after the hack and you can use the Ultrasn0w unlocking tool to unlock your iDevice, later. iPhone unlocks are specific to different baseband versions and hacking the base-band is necessary to allow your device to use the cellular modem. However, it's a tethered jailbreak which means you will have to jailbreak it every time your device loses power or gets restarted.

How it can be done?
1. You’ll need the PwnageTool version 4.3.3 of the iOS firmware; the bundles of PwnageTool specifically for iOS 4.3.4, Mac, iTunes and tethered-boot utility for jailbreaking when you restart.
2. Download PwnageTool bundle and extract it on your system. Select the appropriate bundle for your device and save the bundle file. You may also download PwnageTool 4.3.3 and copy it in the Application directory by right-clicking on the PwnageTool icon and then clicking on 'Show Package Contents'.
4. Copy the .bundle file. Go to folder Contents->Resources->FirmwareBundles and paste it inside the folder. Download iOS 4.3.4 according to your device and save it on your computer.
6. Run PwnageTool in an expert mode, select your device from the list, after which, the application will ask for the firmware. Browse to the location where you saved your iOS 4.3.4, select it, and build it. This will result in a IPSW firmware file.
8. Now you have to get into DFU mode: in order to do that, hold down the 'home' and 'power' buttons together for about 10 seconds and then release the power button for the next 10 seconds. This should land you to the device firmware update(DFU) mode.
9. Go to your Mac and using iTunes select your device. Press the Alt key and click on 'Restore'. Direct the resulting file to the iOS file created using the Pwnage tool. iTunes will update the firmware to jailbroken iOS 4.3.4. After the device boots up, you're into the jailbroken firmware.
Since, this an untethered jailbreak you will need the tethered-boot utility to get into the jailbroken state every time you restart your device.
1. Download the utility and extract the zip file to your computer. Copy the iOS firmware file created using the PwnageTool and change extension from ipsw to zip.
3. Go to the DFU folder located in Firmware and copy files iBSS.n90ap.RELEASE.dfu kernelcache.release.n90 to the tethered-boot utility folder.
4. Turn off your iPhone and run the command sudo on the Mac terminal. The sudo command allows the administrator to give access to other users of the device. Give the password, open the tetheredboot folder and enter the paths of three files located in the tetheredboot folder, on the terminal.
5. You will be asked to put your device in DFU mode. So, hold down the 'home' and 'power' buttons together for about 10 seconds and then release the power button for the next 10 seconds. Now, wait for some time, an exit message will flash on the terminal and the device will reboot to the jailbroken state.
Is it safe?
This method of jailbreaking to iOS 4.3.4 is tested extensively and ensures success. Don't click at 'Check for Update' while restoring your device to iOS 4.3.4 using iTunes. However, in case something goes wrong with your jailbroken firmware you can always rollback to iOS 4.3.3. Apple is currently signing 4.3.3 so you will need to backup your SHSH blobs to validate the previous firmware.
What more can be done to close the loopholes?
The current jailbreak is a tethered one and Apple would be looking for a complete hardware lock-down in the future. The iPhone Dev team is currently working to create the untethered hack that will provide hassle free access to the devices. The team will be even looking for a cordless jailbreak that will be handy in the future.