Despite jailbreaking the iPhone being deemed legal, Apple isn’t going to stop trying to prevent users from jailbreaking the device. Folks have noticed that the latest version of iBooks, version 1.2.1, refuses to open books on jailbroken iPhones. Comex, from the iPhone Dev Team, has explained how the hack works. It seems that before the device loads a DRM-protected book, iBooks will try to run a small program that has been incorrectly signed. Non-jailbroken devices will refuse to run this, but jailbroken devices will load the program without any issues and when iBooks detects that, it will refuse to proceed. It’s speculated that Apple did this in order to protect the content from iBooks being stripped of DRM, but it does seem like another chess move in the never-ending game of cat and mouse between Apple and jailbreakers out there.