System Extension Blocked notification on macOS 10.13 High Sierra


Article ID: 170113


Updated On:


Symantec Products


When installing an Endpoint Protection Small Business Edition (SEP SBE) agent on a Mac with macOS High Sierra 10.13 you receive the notification System Extension Blocked

System Extension Blocked

A program tried to load new system extension(s) signed by "Symantec". If you want to enable these extensions, open Security & Privacy System Preferences. 


This is due to a change in macOS High Sierra. Kernel Extensions (KEXT) that are not signed by Apple are no longer automatically installed by default. As a security measure, macOS now asks the User to allow the installation of third-party KEXTs.


1. During installation, the OS displays the following notification

2. Toward the bottom of the Security & Privacy window, click the Allow button next to the prompt System software from developer 'Symantec' was blocked from loading.