I specifically allow these executables in Norton 360 Firewall:
C:\Program Files\J River\Media Center 23\JRWeb.exe
C:\Program Files\J River\Media Center 23\JRWorker.exe
C:\Program Files\J River\Media Center 23\Media Center 23.exe
rather than the whole directory. In fact, Norton 360 creates the above rules for those programs based on my response to alerts when a new major version of MC is installed.
That seems to be enough for Norton 360, although I probably should allow:
C:\Program Files\J River\Media Center 23\MC23.exe
C:\Windows\System32\MC23.exe
I actually don't exclude the above from the Norton 360 Virus Scanner. I never have. I also don't exclude media file locations from scans. MC works fine without those exclusions.
The above are all for the 64bit version of course. Windows Defender should work with the same settings, but excluding the whole Program and Data folders as Awesome Donkey suggests will also work. Shotgun versus sniper rifle approach.