The U.S. embassy in Paris has taken the unusual step of flatly denying a French report that Washington was responsible for a cyber attack on the Elysée palace shortly before Nicolas Sarkozy was succeeded as president by François Hollande in May this year.
The weekly magazine L'Express said in an article on Wednesday that a hacking attack had successfully inserted a computer worm on terminals of senior advisers to Mr Sarkozy, accessing secret documents and "strategic plans" on their hard disks.
It alleged those hacked included Xavier Musca, then secretary-general of the Elysée — the president's official residence — and now a senior executive at the bank Crédit Agricole . But it said the attack failed to reach Mr Sarkozy because he did not use a computer.
A number of French media reported in July that the Elysée had been hit by a cyber attack. L'Express, citing anonymous sources, said it involved the attackers gaining access by posing as Facebook friends of presidential staffers and tricking them into revealing their Elysée passwords.
The magazine said the worm displayed the same technical power as "malware" known as Flame, able to retrieve files, capture screen shots and use a computer's microphone to record conversations. It said to create a cyber weapon of such power, suspected of use against countries such as Iran, required the financial and human resources of "a big power".
L'Express, citing "several sources", said French investigators had concluded, based on a "cluster of presumptions", that the attack had come from the US.
In an interview with the magazine, Janet Napolitano, U.S. secretary of homeland security, did not confirm or deny the allegations, but said only that "the U.S. has no stronger ally when it comes to security than France".
But the U.S. embassy in Paris issued a statement "categorically refuting" the report. "France is one of our best allies. Our co-operation is remarkable in the areas of intelligence, the maintenance of order and cyber defense," it said.
Asked about the report at a weekly press conference, Najat Vallaud-Belkacem, equality minister and official spokesperson for the government, said she had no "precise information" about the cyber attack, adding, "I don't believe we have any particular worries" that the US may have been involved.
She went on: "To my knowledge it was all repaired very quickly. There was no difficulty."
L'Express said ANSSI, the national information security agency set up under Mr Sarkozy to defend against cyber attacks, took several days to restore the Elysée networks. The agency declined to comment.