Over 100 organizations are believed to have been targeted in the multi-year cyber-espionage campaign, including the United Nations, international labor groups, as well as government ministries from dozens of countries. The operation was revealed on Tuesday by Area 1, a cyber-security company founded by former officials of the United States National Security Agency, and reported by The New York Times.

The compromised cables come primarily from the European Union’s COREU communication network, a Telex-based network that uses teleprinters to exchange text-based messages. The European Union uses the COREU network to transmit information that is classified “limited” or “restricted” between officials representing the executive governments of the European Union’s member states, members of the European Commission, foreign-ministry officials, and other approved parties. Top-secret information (“tres secret” in European Union parlance) is typically not shared on the COREU network. Consequently, the hacked cables contain mostly low-level information. That does not mean, however, that their access by at least one adversary power does not represent a serious security breach. Area 1 said that its forensic examination of the method used by the hackers reveals a set of cyber-espionage techniques that are closely associated with the Chinese People’s Liberation Army (PLA). These clues, in association with the PLA’s long history of attacking Western diplomatic targets, point to Beijing as a very likely culprit behind the attacks, according to Area 1.

The American cyber-security firm said it was able to access the compromised European Union cables and made over 1,100 of them available to The New York Times. The paper reported on Tuesday that the cables reflect increasing tension between Brussels and Washington, as European Union diplomats attempt to get a handle on the unpredictability of United States President Donald Trump. A series of diplomatic cables discusses the whether the European Union should bypass the White House and work directly with the Republican-controlled US Congress, which is viewed as more reliable and responsible. Another set of diplomatic exchanges describes the frustration of the Beijing’s leadership with Trump, which Chinese President Xi Jinping is said to have described to European Union officials as “a bully [engaged in a] no-rules freestyle boxing match”.

The Times said that it notified the European Union of the breach of its diplomatic cables and was told that officials were “aware of allegations regarding a potential leak of sensitive information and [were] actively investigating the issue”. The paper also contacted the White House National Security Council but did not get a response.