Feike Hacquebord, a researcher with security firm Trend Micro said he had found evidence that the spy group, dubbed "Pawn Storm", targeted the Macron campaign with email phishing tricks and attempts to install malware on the campaign site, Reuters reports.
He said telltale digital fingerprints linked the Macron attacks with those last year on the U.S. Democratic National Committee (DNC) the campaign of presidential candidate Hillary Clinton, and that similar techniques were used to target German Chancellor Angela Merkel's party in April and May of 2016.
"We have seen that phishing sites were set up and the fingerprints were really the same actors as in the DNC breach," Hacquebord told Reuters.
Read alsoFrench elections: Macron's headquarters denies accreditation to Russian propagandistsRussia denied any involvement in the attacks on Macron's campaign.
Security experts say Pawn Storm is known to let time pass before leaking stolen documents and that any hacking of Macron's campaign in recent months is unlikely to influence the run-up to the May 7 second round. But, if documents have been stolen, they could be used to undermine Macron's presidency should he win.