Emmanuel Macron’s campaign says it has been the target of a “massive hacking attack” after a trove of documents was released online.
The campaign of French presidential candidate said that genuine files were mixed up with fake ones in order to confuse people.
It said it was clear that hackers wanted to undermine Emmanuel Macron ahead of May 7 second round vote.
The documents were leaked on a file sharing website on May 5 and the Macron camp condemned the action just before the official campaigning period ended at midnight.
Candidates and the media now face restrictions until the polls close on May 7, meaning Emmanuel Macron cannot issue further statements.
Opinion polls had indicated the former economy minister carried a lead of 20 percentage points or more over Marine Le Pen.
About nine gigabytes of data were posted online by an anonymous user.
Emmanuel Macron’s En Marche movement said internal campaign documents, including emails and financial data, had been taken in an “act of massive, co-ordinated hacking”.
“The leaked files were obtained several weeks ago by hacking personal and professional email accounts of several officials of the movement,” the party said in a statement.
The campaign said the documents showed only legitimate campaign activities.
France’s election commission warned that publication or republication of the leaked information could be a criminal offence.
That too remains unclear. The Macron camp has not blamed any specific party but said the hack clearly aimed to damage it and undermine French democracy.
It compared it to the leak of Democratic Party emails in last year’s US presidential election that was blamed on Russian hackers.
WikiLeaks, which published those emails, posted a link to the Macron documents on Twitter but implied it was not responsible.
Emmanuel Macron’s team has already been the victim of hacking attacks, for which it has blamed groups based in Russia and Ukraine. It suspects the Kremlin of wanting to help Marine Le Pen, who supports a pro-Moscow foreign policy.
Macron campaign servers went down for several minutes in February after attacks apparently originating in Ukraine. Last month, security experts from the company Trend Micro said that Russian hackers were targeting Emmanuel Macron’s campaign, using phishing emails, malware and fake net domains in an attempt to grab login names, passwords and other credentials of campaign staff.
Russia has denied that it is behind attacks aimed at Emmanuel Macron.
On May 4, Emmanuel Macron filed a lawsuit over online rumors that he had a secret bank account in the Caribbean.
The centrist candidate called the allegations “fake news and lies” and said some of the sites spreading them were “linked to Russian interests”.
Separate security alerts in and around Paris marred May 5 final scramble by the candidates to court voters.
A suspected radical Islamist possessing weapons and a pledge of allegiance to ISIS was arrested north of Paris.
Greenpeace activists scaled the Eiffel Tower to unfurl a banner, sparking an emergency police meeting.
French voters have rejected the two big political parties – the Socialists and the Republicans – that have governed for decades.
Voters will be making a decision on the country’s future direction and on its place at the heart of the EU.
If they opt for liberal Emmanuel Macron, they will be backing a candidate who seeks EU reform as well as deeper European integration, in the form of a eurozone budget and eurozone finance ministers.
If instead they choose far-right Marine Le Pen she promises quite the opposite. She wants a Europe of nations to replace the EU.
“I give myself six months to negotiate with the EU the return of sovereignty. Then it will be the French who decide,” Marine Le Pen tweeted.
The assumption is that Marine Le Pen would fail and a referendum would take place initially on France’s membership of the euro.
After the Brexit vote in the UK and the election of President Donald Trump, France is the latest country to deal a blow to politics as usual.