Enlarge / An errant update may have disabled your Mac’s Ethernet port recently. (credit: Andrew Cunningham) If you’re having problems with your Mac’s Ethernet port this morning, the culprit may be an errant automatic update that Apple published over the weekend. Luckily, the damage isn’t permanent: an Apple support article posted yesterday will walk you through diagnosing and fixing the problem, which involves connecting to your network via Wi-Fi and running a software update command in the Terminal. If you’re reading this and your Ethernet port is working fine, odds are good that you’ve already installed the follow-up update released to fix the problem. The culprit is an update for the System Integrity Protection feature for OS X, the El Capitan feature that protects some system folders and keeps unsigned or incorrectly signed kernel extensions (or “kexts,” roughly analogous to drivers in a Windows or Linux machine) from loading. In this case, the kext used to enable the Ethernet port on Macs was blacklisted—if you restarted your Mac after applying this update but before your computer had a chance to download the quickly issued fix, you’ll find yourself without an Ethernet connection. This blacklist isn’t updated through the Mac App Store like purchased apps or OS X itself. Rather, it uses a seamless auto-update mechanism that executes in the background even if you haven’t enabled normal automatic updates. Apple uses a similar mechanism to update OS X’s anti-malware blacklist, a rudimentary security feature introduced in 2011 following the high-profile Mac Defender malware infection and occasionally used to push other critical software updates . Read 1 remaining paragraphs | Comments

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OS X blacklist accidentally disables Ethernet in OS X 10.11