While I have not noticed the CPU usage others have reported, nor in 5 years of using various versions have I ever seen SpyBot or Symantec have problems, but Windows Defender doesn't even offer "Allow" as an option for RealVNC and eventually forces a complete uninstall of the server application, despite repeatedly hitting the "Ignore" button in the strange dialog window it pops up when VNC is detected. (I suspect Ultra & Tight will have the same effect.)
I realize this is an obvious sign that Microsoft is jealous that they didn't invent the idea, and that thier own Remote Desktop solution is so unsecure, that any user with a brain will uninstall it on site. But if anybody has a workaround (other than removing Defender), please reply.