Run RedSn0w and point it at the 4.0 IPSW. (Yes – point it at the 4.0 IPSW even though you’re at 4.0.1). This will also hacktivate your iPhone3G at 4.0.1 if you haven’t already been activated by iTunes.
Install ultrasn0w in Cydia (add repository http://repo666.ultrasn0w.com) if you need a carrier unlock (and in the USA, remember to turn off 3G mode in Settings→General→Network).
DevTeam successfully jailbreaked new iOS 4. They updated jailbreak utility redsn0w to version 0.9.5b5-3. Supported devices are iPhone3G and iPod Touch 2G (not MC). New redsn0w is also able to hacktivate iOS 4.0 for iPhone3G.
A new group of hackers claim they found a new exploit for the iPhone 3GS and iPod Touch with the new BootRom. This means that jailbreak for iPhone 3GS (late models) and iPod Touch 2G (MC) and iPod Touch 3G will be available.
We just found an amazing Exploit in the Boot-System of the 3GS with the new Bootrom! This Exploit works on ALL iPhone and iPod Touches!
The tool will be called Gull1hack. The operation is very simple and the code is sent when the device is in recovery mode, just like Blackra1n and Redsn0w do. This jailbreak tool has been neither confirmed by Geohot nor from the DevTeam. Many users think this is fake. We’ll see.
And after the various Key and provocations made by GeoHotz, the DevTeam has decided to write a new article on the official blog with good news for all owners of an iPhone 3GS! The DevTeam has verified that the exploit called 24Kpwn (used for the first time to unlock the iPod Touch 2G) is still valid and it works wonderfully for iPhone 3GS.
It seems the new version of bootrom used by Apple in 3GS dates back in August, a few months before the release of 24Kpwn, so there was no time to solve the problem.
In addition, the new daemon released by the team under the name of ultrasn0w (unlock for iPhone 3G) will work with iPhone 3GS.
New versions of redsn0w (jailbreak) and ultrasn0w (unlock) with iPhone 3GS support will be released soon.