The USA has been accused of hacking into the French government's computer network, in what has been called an "unprecedented cyber attack between allies."
The alleged attack took place on 6 May 2012, during the second round of the French presidential election, nine days before Nicolas Sarkozy lost out to Franois Hollande.
A second attack is also claimed to have been carried out on 15 May, the day Hollande took power.
French magazine L'Express claims the initial security breach occurred after one or more workers at the Elyse Palace clicked on a fake intranet link delivered to them via Facebook's messaging service.
Sources told the publication the hackers passed themselves off as friends of people working for the presidential palace, then invited them to connect to the Palace's intranet via a false link.
The attackers were then able to retrieve the user's log-in details and enter the governmental network "in complete confidence".
Using the stolen details, the hackers allegedly deployed a spyware Trojan similar to the Flame malware, which affected computers of the Iranian Oil Ministry.
Flame was jointly developed by the NSA, CIA and Israeli military, according to the Washington Post, and experts speaking to L'Express claim the attack on the Elyse could only have come from the US government.
The worm infected a handful of machines, however L'Expresse claims some of the people highest up in the Sarkozy government were among those affected, including secretary general Zavier Musca.
The president himself only escaped infection as he did not use a PC.
Mitchell Moss, spokesman for the American embassy in Paris, said in a statement: "We categorically refute the allegations ... [that] the government of the United States of America participated in a cyberattack against the French government. France is one of our closest allies."
The French government declined to comment.
