This software update was pushed via the silent "security updates" to my iMac today: 031-51913 | Incompatible Kernel Extension Configuration Data 3.28.1 After rebooting my ethernet didn't work. Turns out that it added an exclusion for the stock AppleBCM5701Ethernet driver! This breaks ethernet and you have to use WiFi to get online. I rolled the exclusion list back to the last version in my Time Machine backup to fix it, but this required booting from a recovery partition and was a huge pain in the butt, not to mention the time wasted finding the problem. I highly suggest running: softwareupdate --schedule off as root to prevent automatic updates until Apple rolls back this bad update. Hopefully they did so already!