You could write all code yourself for absolutely everything with your own dedicated crew of vetted developers. Or buy closed source from someone like Microsoft

You could write all code yourself for absolutely everything with your own dedicated crew of vetted developers. Or buy closed source from someone like Microsoft, hoping that they have the resources and actually use the resources to scrutinise code more vigorously. And there is always the approach of having a great secops team to detect strange network activity and attempts to escalate.