“Tempesting,” is the verb for hardening a computer installation against radio-wave interception (and/or interference) from TEMPEST. This is a method of side-channel attack whose cost effectiveness has not been easily evaluated by the public.
The known defeat is a Farady Cage, and Embassies are rumored to employ such measures in basement safe rooms, encased in plexiglass.
An anti-static mat might be employed to safeguard components against damage from static electricity during maintenance and repair.
The experiment consists of inserting an anti-static mat (cut to size) in the side of a computer case below (and orthogonal to) the processor, in place of other radio interference measures. This is typically the side that is left secured when exchanging components.
It is to be hoped that this would secure the processor against interception, leaving hard drive controllers and Video Display Units (VDUs) to other safeguards.
Added 1/10: Attaching the grounding wire to the case is an additional variable, which may draw the metallic enclosure into the effect.
Updated 04/09: A friend who is an Electrical Engineer, had a wry response to the above assertions: “Either that, or it eliminates ANY interference, for a crystal clear signal.” I do not possess a working model of the TEMPEST exploit, so I have not been able to perform a repeatable experiment.