After a manual installation or remote deployment of the Resilio Connect Agent 2.11 for Mac on macOS High Sierra (10.13) and later, the operating system shows the System Extension Blocked warning when the Agent is first launched and a Job with Transparent Selective Sync has been added to the Agent. I recently installed the 'Cisco AnyConnect Secure Mobility Client' for my MacBook (OS: High Sierra 10.13.6). Multiple windows of 'System Extension Blocked' are popping up, with the information that 'A program tried to load new system extension(s) signed by Cisco.' If then prompts me to enable the extensions by going to my Security Preferences. When the System Extension Blocked notification appears, click OK. Optionally, untick the box if you do not want Google Chrome installed as your default browser, then click Continue. Click Move to Trash. Click OK to allow the Avast Security installer to access your downloads folder. Avast Security is now installed on your Mac. This article provides instructions to enable kernel extensions that have been blocked during software installations in macOS. Apple introduces a new security mechanism in macOS High Sierra 10.13 that requires a user’s approval before loading third-party kernel extensions (kexts). Several LaCie programs are impacted by this macOS feature.

On another note you really don't need Avast. There are NO known viruses for Macs. All Avast does is lighten your wallet and adversely affect the system performance. You should remove it according to the developer's instruction: Uninstalling Avast Security from Mac | Official Avast Support

Additionally there is absolutely no need for any A/V, 'cleaning', 'optimizing'or 'speedup' apps for the Mac. They are known to do more harm and no good.

This user tip is an excellent treatise on how to protect your Mac: Effective defenses against malware and other threats

May 30, 2018 1:03 PM

macOS High Sierra 10.13 introduced a new security feature that requires manual user approval before loading new third-party kernel extensions.

User Approved Kernel Extension Loading

To improve security on the Mac, kernel extensions installed with or after the installation of macOS High Sierra require user consent in order to load. This is known as User Approved Kernel Extension Loading. Any user can approve a kernel extension, even if they don’t have administrator privileges.

A walk-through of the user approval process

When a user installs an application on a Mac (either from a local source or via Managed Software Center) which loads a third-party extension, the load request is denied and macOS presents the alert shown in Figure 1.

Avast For Mac High Sierra System Extension Blocked Download

Figure 1 — The 'System Extension Blocked' dialog which you would see if you have installed the GlobalProtect VPN application for the first time.

Click on the button labeled 'Open Security Preferences', which will take you to the Security & Privacy panel of Systems Preferences (as shown in Figure 2).

NOTE: If you click the 'OK' button instead, you have 30 minutes in which to navigate to the Security & Privacy System Preference before the Allow button disappears. You would then need to restart the Mac in order to approve the system extension(s).

Figure 2— User approval to load the third-party extension. In this example, selecting 'Allow' will enable loading of kernel extensions from Palo Alto Networks, developers of the GlobalProtect VPN client.

Click on the 'Allow' button to enable the kernel extension to load so that this application (and any other applications by the same developer) will function properly on the Mac. You will be prompted if a restart is required at this time.

Which applications require user approval?

Below is a short list of the third-party applications you would be most likely to encounter at WCER which may require manual approval:

• Box Drive (cloud storage and collaboration application)

• Cisco System's AMP for Endpoints Connector (antivirus and malware protection)

• Palo Alto Networks GlobalProtect (VPN client)

• VMWare Fusion (virtual machine application)

Avast For Mac High Sierra System Extension Blocked Free

Avast For Mac High Sierra System Extension Blocked Windows 10

PLEASE NOTE:If any of these applications were already installed when you received your Mac, then the Tech Services administrator would have already approved them so you should not be prompted for approval.