Analysis by security firm FireEye and reported today by Reuters reveals that Chinese hackers sent e-mails to staff of the European ministries with files containing malware.
The hackers infiltrated the ministries' computer networks by sending emails to staff containing malicious files with titles such as "US_military_options_in_Syria," which infected the networks when recipients opened these documents.
For about a week in late August, California-based FireEye said its researchers were able to monitor the "inner workings" of the main computer server used by the hackers to conduct their reconnaissance and move across compromised systems.
FireEye, which describes itself as the 'leader in next generation threat protection', lost access to the hackers after they moved to another server shortly before the G20 Summit in St. Petersburg, Russia. The anti-virus company said it believes the hackers were preparing to start stealing data just as the researchers lost access.
The company refused to identify the nations whose ministries were hacked, although it said they were all members of the European Union. The US was seemingly left alone.
FireEye said it reported the attacks to the victims through the FBI. FBI spokeswoman Jenny Shearer declined to comment to Reuters.