Gavin de Becker, Jeff Bezos’ longtime security chief, may run his own consulting firm, write books, operate a private luxury terminal at Los Angeles International Airport and develop threat-assessment tools.

But he is really selling only one thing: peace of mind.

For more than four decades, Mr. de Becker, 64, has counseled the United States government, law enforcement departments, thousands of celebrity clients and countless readers on how to ward off threats and stay safe in a scary world.

His most recent case was for Mr. Bezos, Amazon’s chief executive, who asked him to find out how American Media Inc., which publishes The National Enquirer, had obtained private intimate pictures of Mr. Bezos and his girlfriend, Lauren Sanchez.

[Mr. Bezos’ claim brought intrigue and politics to The Enquirer’s exposure of his extramarital affair.]