TOKYO — A Chinese AI cybersecurity tool called Artex was used in a spate of recent hacks of Japanese companies, the subsidiary of a major Tokyo-based internet company said Tuesday. Dozens of Japanese companies, from restaurant chains to a car hire operator, have disclosed unauthorized access or data breaches in recent weeks -- potentially impacting millions of customers. The information security arm of GMO Internet Group said it had "confirmed Artex was used" having investigated the attacks in collaboration with external organizations. "It also became clear... the attacks were almost exclusively targeting Japan," Daiki Fukumori of GMO wrote on the company blog. AI's ability to find previously unknown ways to hack into computer systems is in the global spotlight, as leading labs release ever-more advanced models. Artex was designed to help organizations strengthen their cyber defenses through AI-powered security testing to find potential weak points, its developer has said. The Chinese tool this month stopped programmers from accessing its source code, acknowledging misuse by "bad actors"