Can a network interface be activated if the ifcfg-files are missing?

I have a RHEL/CentOS7 installation with some unused network ports. NetworkManager is not in use on this system, only the legacy "ifupdown" network scripts. I would like to "disable" the unused network ports to prevent accidental use, and I have considered simply deleting the corresponding /etc/sysconfig/network-scripts/ifcfg-* files. I know that the interface can then no longer be activated manually via ifup, but I want to be sure that there is no "default" behavior which would allow a (non-root) user to plug in a network cable and then get these interfaces working anyway. **So the question is:** Can a network interface be activated by a non-root user (e.g. due to some automatic fall-back behavior) under legacy network scripts if there is no ifcfg- file corresponding to that interface? (Alternative formulation: What is the default behavior of a network interface if there is not ifcfg- file for it?)