A telephone network interface device (NID) isolation module (NIM). The NIM is adapted to fit a telco-side modular jack of a NID bridging a telco feed to inside wiring. The NIM comprises a modular plug made of an electrically insulating material that fits securely in the modular jack. Following disconnection of the telco feed from the inside wiring, the NIM is inserted into the modular jack to prevent the reconnection of the telco feed to the inside wiring. A tag component of the NIM is used to provide instructions and warnings to a subscriber or a service technician relating to the use of the telco-side modular jack.