LONDON — Heads of the FBI and the British Home Security Service issued strong warnings to business leaders about the threats posed by Chinese espionage, especially espionage aimed at stealing the intellectual property of Western technology companies .
In a rare joint appearance Wednesday at MI5 headquarters, Christopher Wray, director of the Federal Bureau of Investigation, and Ken McCallum, general manager of MI5, urged executives not to underestimate the scale and sophistication of the Beijing campaign.