At a San Francisco playground, a stranger tried to befriend an OpenAI employee who was there with their child. The stranger also regularly showed up with a child, and, in the process of making small talk, asked the OpenAI employee questions about their work. It was no idle curiosity: The stranger was a spy. That is one of the scenarios employees of the artificial intelligence company have been presented with in attempts to raise their vigilance against attempts to steal corporate secrets—and that was before federal authorities arrested an employee for planting a listening device. In training sessions, OpenAI has…