Hackers, probably Russian, have exploited a bug in Microsoft Windows and other software to spy on computers used by NATO, the European Union, Ukraine and companies in the energy and telecommunications sectors, according to cyber-intelligence firm iSight Partners.

ISight said it did not know what data the hackers had found, but it suspected they were seeking information on the Ukraine crisis, as well as diplomatic, energy and telecommunications data, based on the targets and the subject-matter of infected emails sent to victims. The emails injected tainted code into the computers.

The five-year cyber espionage campaign is still ongoing, iSight said, dubbing the operation "Sandworm Team" because it found references to the "Dune" science fiction series in the hackers' software code.