The Mac has avoided widespread malware, and Apple tries to keep ahead of the ways in which malicious software can gain a foothold in macOS. In 2015 with El Capitan, that was System Integrity Protection, to keep system files from being modified. Sierra in 2017 removed an option to allow unsigned Mac apps to run without a prompt.
Now in Mojave, macOS has forced apps to request certain kinds of system-level privileges for behavior that it generally allowed in previous releases. In some cases with older apps that haven’t been updated, you have to take a manual step to keep them working, too.
If you have any of these apps installed, after upgrading to Mojave you will receive prompts or warnings from them, explaining that you have to approve or add them to the Security & Privacy system preference pane’s Privacy tab. In some cases, apps need a check in a box next them in the Accessibility list; in others, in Full Disk Access. Macworld reader David wonders about the difference.
For both kinds of permission, an app or macOS should prompt you or explain how to proceed. You shouldn’t have to figure out on your own whether you need to add permission or add an app to the list. Mojave is still new, so some developers are still releasing compatibility updates to streamline how they request permission from you.
Read more at Macworld.com