Ultrasn0w is available through the Cydia unofficial app store, for which you’ll need a jailbroken handset in order to install and access.  That can be done using JailbreakMe, a simple online interface whereby sliding a single control automatically takes your iPhone 4 through the jailbreak process.

Currently ultrasn0w works with iPhone4 baseband 01.59 (along with iPhone 3G/3GS basebands 04.26.08, 05.11.07, 05.12.01 and 05.13.04); if you’re having trouble finding it in Cydia then you may have to add the repo666.ultrasn0w.com repository.  If you’re thinking of trying it, it’s worth bearing in mind that Apple don’t look kindly on jailbreaking and may void your warranty; as ever, hack at your own risk.

“Every Push application has to request the unique token from the Apple’s APNS servers to identify the device it’s running on. Thanks to that token, APNS servers always know which device is yours … On any unlocked iPhone, the application requesting the token is stuck. APNS does not provide any response at all and the application can either cancel the request completely by automatic timeout or let user wait with the progress bar forever. Either way, the user will never receive any Push message, because APNS has not provided the token.” PoweryBase

PoweryBase are now advising those users with unlocked devices not to buy their app, as they will not be able to promise Push Notification functionality.  In the same way, such users should not expect any APNS-reliant service to work as advertised, unless Apple change their support policies.

The iPhone Dev Team are aware of the issue, and have already released one trial fix for affected devices.  However it still needs work, and a stable release is still not available; hopefully at some future point it will be integrated into their ultrasn0w unlocking app.

[via MacRumors]

“We realize we upset some folks (e.g. existing 3GS owners) with our earlier announcement that we wanted to hold onto the 3GS iBoot-family hole until 3.1 was out. Our aim there was to get as many people as possible onboard (within reason of course) before revealing the hole, since Apple will fix it immediately. But all of that became moot when the purplera1n release was made, since it uses the same hole” iPhone Dev Team

Those wishing to unlock their iPhone – and keep it unlocked – are still being warned to avoid Apple’s official baseband updates.  The Cupertino company has apparently stepped up its efforts to remove loopholes such as the one which enables this latest version of ultrasn0w. 

Going by the comments over at the Dev Team blog, however, Apple retaliation is not the only problem some users are facing.  Some iPhone 3GS owners are experiencing poor signal reception after unlocking, or an inability to connect to WiFi networks, while others claim their handsets have been left bricked or show significant battery drain.  Now seems as good a time as any to warn that Apple are unlikely to perform warranty repairs on any iPhone they believe has been tampered with, so you attempt a jailbreak or carrier unlock at your own risk.

[via iPhoneBuzz]

“Here’s the critical point, the reason why we’re delaying our version of the jailbreak: Once the jailbreak is out, Apple will fix the iBoot-family bug we use to accomplish it.  They will simply stop signing the old iBoots and only sign the fixed ones.  If you bought your phone after Apple has done this, there’s nothing you can do…the jailbreak isn’t going to work for you.” iPhone Dev Team blog

According to the Team, the exploit depends on an iBoot-family bug, which can only be addressed if users have a signed iBoot-family img3 from their own device.  This contains their ECID, a unique chip identifier different on each iPhone 3GS.  If Apple discover the loophole, they could update the smartphone and refuse to sign any old iBoots; then those users would not be able to jailbreak or unlock their handsets.

The Dev Team are counting on an imminent iPhone OS 3.01 update which addresses some of the platforms more buggier aspects, and are waiting until then to see the state of play.  They’ve given no indication of when the iPhone 3GS jailbreak and unlock option might be released, a situation that’s prompting no small amount of revolt in their comments.

The loophole arose, the Team believe, because Apple finalized the iPhone 3GS’ bootrom in around August 2008, months before the exploit was identified for the iPod touch 2G.  24Kpwn went on to be exploited in the redsn0w tool, and similar techniques can now be implemented in ultrasn0w.

It will take some time to update ultrasn0w with the new system, but once completed it will mean the iPhone 3GS can not only be loaded with unofficial apps but used with any SIM card.  Apple are likely to release a firmware update to try to prevent any damage, so the Dev Team are advising that people avoid baseband updates.

[via iPhone Buzz]

Redsn0w will unlock an original iPhone, but not the 3G version, as well as jailbreaking both generations of iPod touch.  Together, the Team claim that they can now unlock any iPhone 3G or iPhone, even those that previously proved impossible.

However Ultrasn0w does not, as yet, work on the new iPhone 3GS.  This functionality is apparently on its way, but for the moment owners of the new smartphone shouldn’t attempt to use Ultrasn0w.