System Extension Blocked - warning

After upgrading your macOS computer to High Sierra 10.13.4 or higher (starting in April 2018), you may see a message about a System Extension Blocked.  At Williams we have seen this warning appear for these programs:

  • Sophos Anti-Virus
  • Cisco VPN
  • VirtualBox



If you see the Open Security Preferences button, click that, then click Allow.

If you only see OK, click that then go to your Apple Menu:  System Preferences: Security and Privacy.  Click Allow.


You should only need to do this once and only for the few applications which have not certified their programs with Apple.  These will be resolved soon by the vendors.