While 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

This is due to a change made in macOS High Sierra with loading Kernel Extensions (KEXT).

macOS High Sierra 10.13

1. During installation, the OS displays the following notification

2. Complete installation. After reboot, you will receive a notification informing that you are at risk and need to Finish Setup (you may also see a Retry or Finish Setup button).

3. You will be prompted to open the Security & Privacy window of System Preferences (you can also open System Preferences and navigate to Security & Privacy> General).

4. 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.

5. A message to reboot will be displayed. This is necessary to enable the full protection features in the product.