Thousands of communications have been intercepted during an attack that spanned three years across a range of international matters, including Donald Trump and global trade, The New York Times reports.
The breach was reportedly discovered by Area 1, a security firm founded by former NSA officials, which found that hackers had gained access to a European communications database following a rudimentary phishing campaign.
Hackers are believed to have initially targeted diplomats based in Cyprus, which gave them access to the country's communication system and a list of passwords for the wider EU network. Initial analysis of the infiltration has led researchers to believe it was orchestrated by the Chinese state.
"After over a decade of experience countering Chinese cyberoperations and extensive technical analysis, there is no doubt this campaign is connected to the Chinese government," said Blake Darche, an expert from the security firm speaking to the NYT.
"People talk about sophisticated hackers, but there was nothing really sophisticated about this," Owen Falkowitz of Area 1 said to the NYT.
No sensitive or confidential information was obtained during the attack; highly secretive documents including a level called "tres secret" are held on a separate system which is currently being upgraded and replaced, said European officials.
The messages, known as diplomatic cables, were all low-level communications but details of them reveal concerns about the unpredictable Trump administration, struggles to deal with Russia and China, and the risk that Iran would revive its nuclear program.
One cable depicted a meeting between President Trump and Vladimir Putin in Finland and was described as "successful (at least for Putin)".
Another cable detailed a report of a meeting between European officials and President Xi Jinping of China who likened Tump's bullying of Beijing to a freestyle boxing match and that China would not submit to such bullying "even if a trade war hurt everybody," highlighting the tensions between the two nations' widely-reported trade war.
Another quotes reports of European diplomats saying Crimea had been turned into a "hot zone where nuclear warheads might have already been deployed", but American officials say they have not seen evidence of warheads in Crimea.
Over 100 other organisations institutions, including the United Nations, were also affected by the breach and have been alerted. Some of the UN's material is related to private meetings between the secretary-general and his deputies with Asian leaders in the months where North Korea was testing missiles in 2016.
The NSA had reportedly previously warned the EU repeatedly that the legacy tech it used for its communications system was prone to hacks from other nations, advice that was seemingly ignored.
The Chinese embassy has not responded to our request for comment at this time.
