When will automotive industry investors learn the lesson from this weekend's reported drone attack on a Saudi oil facility? 

We saw one version of this kind of scenario in the 1977 movie "Telefon" with Charles Bronson: Brainwashed sleeper cells were sent out in trucks to smash into various critical facilities, causing huge explosions.

The attack on the Saudi oil facility explains why it's illegal to operate a drone near an airport or a city center anywhere in America today. The risk of terrorist sabotage is simply too high.

But what is a driverless car, if not a 5,000-pound, land-based drone? We saw it not only in "Telefon" but also in car/truck bomb events in Afghanistan and Iraq over the last 10+ years.

Automakers can crow all they want about their intent to make their future driverless vehicles unhackable. Gee, why didn't anyone think of making a connected computer unhackable before? Please, someone call Microsoft, Apple, Google, Dell, Hewlett-Packard or any of the other computer industry entities and inform them about this revolutionary -- and easy-to-implement -- idea.

The fact is, there is no such thing as an unhackable connected computer, and there will never be. Thinking that one can be created is as futile as attempting to ban human stupidity. It's in the nature of things, and can't be wished away.

It's not only about driverless cars being hacked. Numerous Chinese brands have been salivating for years to export their soon-to-be driverless cars to the U.S. Those cars are "electric and connected" today -- and would become "driverless" when the software has "been perfected."

Then, they will be "turned on" -- or remotely upgraded -- to full driverless capability. Sort of like the sleeper cell telephone call in "Telefon."

You ought to be able to conclude from this that neither driverless cars -- of any origin -- nor Chinese cars of any kind, will ever be allowed to be sold or operated in the U.S. They constitute an even graver threat to U.S. national security than the presence of a Huawei switch in a U.S. telecom network such as AT&T or Verizon.

The message for the world's automakers and their investors is clear: When it comes to driverless cars, give it up. It's a futile exercise. If they are ever made to work, they must be immediately banned for national security reasons.

This weekend's drone attack in Saudi Arabia is yet another piece of evidence of why this is the only logical conclusion. A driverless car is just a very large land-based drone that can carry a lot more weight.

For all the automakers and other technology companies who are pursuing the pathway to driverless cars, ranging from Alphabet (GOOGL) - Get Report , Ford (F) - Get Report , Tesla (TSLA) - Get Report and General Motors (GM) - Get Report just to mention some of the more prominent ones, the futility of this outcome points to a multi-billion dollar write-off in the end.

The question is only how quickly such a write-off will have to be realized -- will it be closer to two years from now, or ten years from now?

Alphabet is a holding in Jim Cramer'sAction Alerts PLUS Charitable Trust Portfolio. Want to be alerted before Cramer buys or sells GOOGL? Learn more now.

At the time of submitting this article for publication, the author was short TSLA and long F, GOOG and GOOGL. However, positions can change at any time. The author regularly attends press conferences, new vehicle launches and equivalent, hosted by most major automakers.