All connections to the corporate network must be secured and encrypted
It should not be possible to obtain internal data via your network connection simply by intercepting the data as they pass through a cable. Network access control, augmented by a permanent and transparent encryption, prevents this type of attack.
Introducing non-certified hardware in the network, connecting such hardware without anyone’s knowledge, and even intercepting data are typical loopholes in network security. Strict access control (e.g. based on MAC addresses) and permanent encryptions are recommended.