Under China’s authoritarian leader, Xi Jinping, Beijing has refined its approach to cyberspying, transforming over the past decade into a far more sophisticated actor. China’s premier spy agency, borrowing a page from Russia, has recruited beyond its ranks, pulling from the country’s growing pool of tech workers. The strategy has made its attacks more scattershot and unpredictable, but analysts say it has also helped strengthen the country’s efforts, enabling spies to run stealthy attacks that target intellectual property as well as political and military intelligence around the world. Mr. Xi has made improving China’s scientific and technical capabilities a priority…