An external device such as this shield by MIT has a number of advantages over securing the devices themselves.

FORBES: Protecting Pacemakers From Hackers

To protect electronics infrastructure, entire systems must be encased in a metallic shield to prevent any external electromagnetic pulse from entering.

CENTERFORSECURITYPOLICY: Old threat with a new face

To protect electronics, an entire system must be encased in a metallic shield that prevents any external electromagnetic pulse from entering.

CENTERFORSECURITYPOLICY: Center For Security Policy

Regulators want to safeguard the strength and soundness of the banks they supervise, so they tend to shield them from the full force of domestic or external competition.

ECONOMIST: Open wider | The