CMMC Practice AC.1.003: Verify and control/limit connections to and use of external information systems.
CMMC CLARIFICATION (Ref CMMC – Appendix B)
Make sure to control and manage connections between your company network and outside networks, such as the public internet or a network that does not belong to your company. Be aware of applications that can be run by outside systems. Control and limit personal devices like laptops, tablets, and phones from accessing the company networks and information. You can also choose to limit how and when your network is connected to outside systems and/or decide that only certain employees can connect to outside systems from network resources.