A recent Apple security update silently pushed to iMacs on Friday, February 27, is breaking Ethernet drivers around the world, as Mac users have discovered.



"After rebooting my ethernet didn't work. Turns out that it added an exclusion for the stock AppleBCM5701Ethernet driver!" users complain online.
For the past two days, users have been sharing tips on how to avoid having their Macs wrecked. For users who had still not yet received this update, the easiest way to avoid problems was to turn off their auto-update feature. This can be done by running "softwareupdate --schedule off" as root in a terminal window.
Users who got the update were encouraged to roll back their Macs to a previous version, not affected by this issue. And then disable the auto-update issue.
The update, labeled as "031-51913 | Incompatible Kernel Extension Configuration Data 3.28.1" only affects Ethernet drivers, not WiFi, meaning users can still get online without any problems.
Apple's staff eventually caught on that something was wrong, and today, February 29, have issued another update, 3.28.2, which fixed what 3.28.1 had broken.
If users have access to a WiFi connection, the update will be installed automatically when they come online for the first time. For people who don't have a WiFi network running at their home or work, Apple's support team has published instructions on how to restore a previous version of the Ethernet drivers folder from an older backup. The instructions can be viewed by pressing the button below.