The iPhone Dev-Team has released the updated version of their Jailbreak tool RedSn0w which is now capable of jailbreaking the newly released iPhone OS 4. There have been many attempts and announcements as well as videos promising the released of updated versions of other jailbreaking tools like Sn0wbreeze, Blackra1n and others that would support the new iPhone OS 4 but the Dev-Team are the first ones to release their working version of iPhone OS 4 jailbreak tool.
Important
Now you can do untethered Jailbreak of your iPhone 3G/3Gs running latest firmware 3.1.3 with "Spirit".
Step by Step iPhone 2G/3G/3Gs Firmware 3.1.3 Jailbreak Guide Using Spirit
The tool will only help those who have upgraded their iPhone 3G and 3Gs to iPhone OS 4. Even in this case if you have unlocked your iPhone using an old baseband since upgrading to the latest iPhone OS 4 will upgrade your baseband as well which will prevent unlocking.
What You Need:
1) Latest iTunes 9.1 for Windows and Mac (Download)
Note: The jailbreak works for iPhone 3G only at this point in time and is for Mac OSX only.
Update:
For upgrading to iPhone OS 4 you need to have an Apple Developer Account with a valid UDID since you will be asked to enter it while upgrading to the new iPhone OS 4 from OS 3.1.3 or older OS.
Once again, this jailbreak is valid for iPhone 3G running iPhone OS 4 and you should have valid UDID.
[via BlogsDNA]