The report, published in the newsmagazine l'Express, said computers of several advisers to then-President Nicolas Sarkozy were compromised in May by a computer virus that had the earmarks of Flame, allegedly created by a U.S.-Israeli team to target Iran's nuclear program, The Hill reported Tuesday.
French officials, speaking anonymously, pointed to the United States.
"You can be on very good terms with a 'friendly' country and still want to guarantee their unwavering support -- especially during a transition period," a French official told the newsmagazine.
The alleged hacking occurred a few days before the second round of the French presidential elections, which Sarkozy lost to Socialist Francois Hollande.
Homeland Security Secretary Janet Napolitano reportedly told l'Express the United States has "no greater ally than France."
"We cooperate in many security-related areas," she said. "I am here to further reinforce those ties and create new ones."
Napolitano also said the Flame and Stuxnet viruses had "never been linked to the U.S. government."
The Hill said the White House did not return a request for comment.