Bloomberg's Michael Riley and Dune Lawrence report: 

The hackers clocked in at precisely 9:23 a.m. Brussels time on July 18 last year, and set to their task. In just 14 minutes of quick keyboard work, they scooped up the e-mails of the president of the European Union Council, Herman Van Rompuy, Europe’s point man for shepherding the delicate politics of the bailout for Greece, according to a computer record of the hackers’ activity.

Over 10 days last July, the hackers returned to the council’s computers four times, accessing the internal communications of 11 of the EU’s economic, security and foreign affairs officials. The breach, unreported until now, potentially gave the intruders an unvarnished view of the financial crisis gripping Europe.

And the spies were themselves being watched. Working together in secret, some 30 North American private security researchers were tracking one of the biggest and busiest hacking groups in China.

Observed for years by U.S. intelligence, which dubbed it Byzantine Candor, the team of hackers also is known in security circles as the Comment group for its trademark of infiltrating computers using hidden webpage computer code known as “comments.”

The group's targets included everyone from British Tobacco companies, to human rights NGOs to -- bizarrely -- an Italian restaurant in midtown Manhattan. According to a 2008 WikiLeaks cable, U.S. officials belief Byzantine Candor is linked to the Chinese military.

In Brussels, the group also stole e-mails from senior trade, foreign policy, and counterterrorism officials. At the time of the breach, the EU was involved in talks on the second Greek bailout.