The real culprit was apparently a recent release of Google’s Keystone software, which is included in its Chrome browser to automatically download updates of the browser. On computers that had Apple’s System Integrity Protection disabled, the update corrupted the computer’s file system, making it impossible to reboot. System Integrity Protection is an Apple technology that is meant to ensure that malicious software doesn’t corrupt core system files. Google advised affected users on how to uninstall the Chrome update, and also suggested that most users may not be at risk at all. “If you have not taken steps to disable System Integrity Protection and your computer is on OS X 10.9 or later, this issue cannot affect you,” the forum post reads. A possible connection to Chrome was first detailed on the Mr. Macintosh blog Tuesday afternoon.As for why several Hollywood studios were hit the hardest, one theory suggests it’s because many of the video editors had to disable System Integrity Protection in order to work with external audio and video devices that are common in professional editing setups.
Variety also suggests that the hardware dongles used for licensing Avid may have played some role in the shut-downs.