Tempest in a Desktop

One day while working at the store, I got a phone call from a regular customer, who was having a problem with one of his Zenith computers. I talked to him a bit, but couldn't do anything for him over the phone so I told him to bring it in, we'd take a quick look at it and see if it was something I could fix at the desk...if not, we'd have to check it in for service.

An hour or so later, the familiar customer walks in wearing unfamiliar clothing -- he's obviously military. He's got his machine tucked under his arm, he greets me, puts the computer on the desk, and pops the cover off -- no screws installed (hey, that's how my computer normally was!).

From the outside, the computer is very normal looking -- a Zenith Z-151. The inside, however, I'd never seen anything like it. Every significant part in the machine had some kind of metal cap over it. What the heck?

"Is this a TEMPEST machine?"

Most of the time I worked at Heathkit, our parent company, Zenith Data Systems, was a major government contractor.
As early as World War II, it was discovered information could be extracted from the signals that computers and other data processing equipment radiated. As a result, many military computers were upgraded to "TEMPEST" security standards, which greatly reduced the radio emissions from the computers of the day. These reductions were made through various techniques, but metal cans over everything would certainly be A way that would help. Needless to say, this was during the cold war, the people authorized to look at these machines did NOT include me or anyone else in our store.
And yes, Zenith sold TEMPEST computers. Apparently. I'm not sure I knew that before this.

My boss had the most amazing hearing -- I think he kept tabs on everything going on at the store at all times from his office. He came flying out of his office, screaming at me, "DON'T TOUCH IT!!! DON'T TOUCH IT!!!!" He then calmed down slightly when he saw I didn't have a screwdriver in my hand, and turned to the customer and explained that we weren't allowed to do anything with those systems -- we didn't have parts, couldn't get parts, and weren't authorized to even look at them, this was all pretty hush-hush stuff (the existence of TEMPEST security shielding wasn't secret, but how it was done very much was).

The customer apologized, put the cover back on, and left.

A couple hours later, the phone rang, it was Corporate wanting to know why we had our noses in a TEMPEST computer. Ok, that's just a little creepy. However, apparently what happened is this person was able to tuck the broken computer under his arm and walk out the front gate with it without issue. On the way back to the office however, THAT'S when they stopped him and asked why he was carrying a machine with secret technology ONTO the base. That's when the base security people called their superiors, the superiors called Zenith, Zenith called Heath, Heath people called us.

since 2/14/2021