redsn0w Jailbreak for iOS 4.2.1 Hits the Web

With iOS 4.2.1 available for only a day, the iPhone Dev Team has already released redsn0w 0.9.6b4. The jailbreak hack, released on Tuesday, lets iPhone, iPad and iPod touch users install apps that aren’t available in Apple’s iTunes-based App Store.

The hack installs just as easily as previous versions, although owners of newer iOS devices will have to tether — meaning connect their device to a computer when booting — to maintain the jailbroken state. Owners of older iOS devices, however, can boot their jailbroken devices without connecting to a computer.

The iPhone Dev Team is warning jailbreakers to avoid the iOS 4.2.1 update if they have also unlocked their iPhone for use on carrier networks that Apple hasn’t partnered with.

Like all hacks, Apple won’t offer support should something go wrong, so don’t try jailbreaking unless you know what you are doing.