Chinese hackers have reportedly compromised a network used by European Union countries to relay diplomatic messages, allowing the intruders to spy on sensitive correspondence about everything from foreign policy to trade to weapons. The intrusion into the EU network, known as COREU, was part of a coordinated cyber-espionage campaign that also breached more than 100 organizations, including the United Nations, various ministries of foreign affairs, labor unions, and think tanks, according to Area 1, a cybersecurity firm based in Redwood City, Calif.