A new "jailbreak" for the iPhone 3GS and iPad was released this weekend by hackers, and allows users to run third-party software with features not authorized by Apple, including multitasking.

Dubbed "Spirit," the software for Windows and Mac OS X allows users to jailbreak their iPhone OS device, including firmware 3.1.2, 3.1.3, and the iPad-exclusive 3.2. The practice of jailbreaking allows users to run code not approved by Apple on their mobile device.

The hack was released by a coder who goes by the handle "comex," and is a member of the Dev Team group. They, along with George "Geohot" Hotz, are the most high-profile hackers of the iPhone OS.

The Spirit jailbreak was first demonstrated on the iPad in early April. The release was delayed until after the iPad 3G went on sale last Friday to ensure it would work with the new hardware.

The jailbreak installs Cydia, an unauthorized digital storefront that is the hackers' equivalent of Apple's own App Store. It includes unauthorized software such as "Backgrounder," which allows users to run more than one application at once. Early reports indicate that Backgrounder works on the iPad, though most other Cydia software created for the iPhone must be updated to run on the larger 9.7-inch screen.

Previously, many iPhone 3GS users could only use a "tethered" jailbreak released by Hotz. This method meant users of the latest iPod touch, and any iPhone 3GS released in October 2009 or later, could not perform a hardware reset of the phone without connecting it via USB cable to a computer. The Spirit jailbreak is not tethered.

Last year, Apple updated the BootROM for the iPhone 3GS to iBoot-359.32 in a mid-cycle hardware release in October — the first time ever that the handset maker modified its hardware in the middle of a product line, without a new model released. That update has slowed hackers in their ongoing game of cat and mouse with Apple.