- Vulnerability, Exploit: geohot
This is geohot's latest jailbreak utility. It is an updated version of purplera1n but now uses geohot's implementation of the usb_control_msg(0x21, 2) Exploit. It has been released for Windows and undoubtedly a Mac version is to follow. It will jailbreak all devices on 3.1, 3.1.1 and 3.1.2. It will even jailbreak OTB iPhone 3GS and iPod touch 3G.
blackra1n does not support hacktivation, so it will your iPhone will need to be officially activated.
How about a 3G/3GS unlock?
At this moment in time, geohot's only unlock is purplesn0w, which only supports the 3.0 baseband. (ultrasn0w only supports the 3.0 baseband also.) And once you update (the baseband), there's no going back for most.
How to use
All you have to do is head to the blackra1n website and download the application on to your computer. Then, plug in your iDevice and press "Make it ra1n". Then you wait. If the phone is stuck in DFU, just press "make it ra1n" again.