As Marine Le Pen sat across the table from Vladimir Putin in a surprise visit to the Kremlin in March, the ex-KGB strongman flashed a smirk as talk turned to hacking.

Amid rumours Russia was again meddling in a democratic contest, Mr Putin assured the contender for the French presidency he would remain hands-off in the nation's unfolding election.

"We do not want to influence events in any way," Mr Putin said, raising his palms as if to signal he would not reach for the hacking toolkit Russia wielded against the US in the 2016 election.

But just over a month since the pair's controversial face-to-face meeting, evidence of covert Russian meddling in France's presidential race is mounting.

And just as Russia is believed to have sought a Donald Trump victory last November, it would appear former National Front leader Ms Le Pen is the Kremlin's favoured candidate ahead of the ballot this Sunday night.

Sorry, this video has expired Macron and Le Pen trade blows in acrimonious final face‑off

Hacking, phishing and fake news

Last week, the "digital fingerprints" of hacking group Pawn Storm were linked to 160 attacks on Ms Le Pen's presidential election rival Emmanuel Macron's email server and website.

Campaign staffers have been targeted with "phishing" emails encouraging them to visit bogus websites designed to break into their accounts, cyber security firm Trend Micro said in a report.

There is no evidence any sensitive data from the election frontrunner has been leaked, the report said.

Pawn Storm, also known by other names including Fancy Bear, is the Moscow-linked group US authorities believe hacked the Democratic National Committee's computers, leaking damaging emails from inside Hillary Clinton's campaign.

And the similarities to the US campaign do not stop there.

Claims of a widespread campaign of "fake news" have emerged as a deluge of articles from state-backed Russian media translated into French wash over social media.

Mr Macron — a young, married former investment banker — has already been forced to deny he had a secret gay relationship with radio executive Mathieu Gallet and that he is backed by a "very rich gay lobby".

Meanwhile, Mr Macron's decidedly more pro-Russian rival Francois Fillon — whose scandal-plagued campaign did not survive the first round of the run-off election last week — appeared to benefit from fake news.

One article claimed Mr Fillon had staged a miraculous recovery in the polls, despite his campaign languishing in third place according to numerous credible voter surveys.

The Kremlin has denied any involvement in the hack, but the suggestion of clandestine Russian interference in western elections to advance its own interests is worryingly familiar.

Does Putin favour Le Pen?

Ms Le Pen's closeness with the Kremlin goes beyond photo-ops with Mr Putin, whom she openly admires.

Her party is believed to have received $12 million in loans from Russian banks in 2014 to fund their election activities, after numerous French and European banks would not give them the money.

Lowy Institute's Herve Lemahieu said if Russia's involvement in the French election were proven, it makes sense that Mr Putin favours a Le Pen victory.

Mr Lemahieu said any attempt to weaken European integration is in Russia's interests.

"What the Russians really don't like in Europe is cohesion and unity of action between the European Union (EU) players because that makes them much stronger as a bloc," he told the ABC.

Ms Le Pen wants hardened borders and to radically renegotiate France's membership of the EU, while Mr Macron wants France to remain engaged with the trading bloc.

Ms Le Pen has called the sanctions levelled at Russia after its invasion of Crimea "completely stupid".

Her hardline stance against the EU is widely seen as favouring Mr Putin's strategic interests in Europe, where Russia is actively stoking nationalistic sentiment to sow discord.

The National Front party manifesto proposes six months of talks with EU partners aimed at creating a loose cooperative of countries.

A referendum would then follow, in which she would recommend leaving the union if her party had not achieved its goal.

In contrast, Mr Macron would likely continue France's efforts to contain Russia's influence in Eastern Europe and would look to maintain sanctions against Moscow over the Ukraine crisis.

"There is a natural ideological symmetry between Mr Putin and Ms Le Pen, and Mr Macron is the ideological opposite of that," Mr Lemahieu said.

How Le Pen could help Russia

Richard Maher from the European University Institute said if made president, Ms Le Pen could recognise Russia's seizure of Crimea.

"Even if Le Pen does not win [as seems likely], her candidacy is a rebuke to the euro, the EU, and the entire French establishment," he said.

"She can be a very disruptive force even if she does not win."

The Russian Government's ability to use hacking attacks to influence French politics assumes the hackers found anything damaging.

Cyber security analyst Zoe Hawkins from the Australian Strategic Policy Institute said it was not clear they did find anything to make the operation worthwhile.

But Pawn Storm is known for not releasing sensitive information immediately and could be planning to use anything it has found as a lever to destabilise Mr Macron once he is in office.

Such a move would force him to focus on shoring up domestic support instead of attending to foreign policy.

"There is value from a Russia perspective in undermining the credibility of democratic institutions," she said.

This Sunday night Australian time, Emmanuel Macron will go head-to-head with Marine Le Pen. ( Reuters: Eric Gaillard )

But it could all backfire for Le Pen

Even if the cyber attacks were intended to weaken her rival Mr Macron, it could backfire and instead undermine Ms Le Pen's bid for the French presidency.

Confirmation that Mr Macron's campaign had been hacked could reflect poorly on Ms Le Pen, according to Ms Hawkins.

That is especially the case if no damaging information about her opponent comes to light and he instead demonstrates his team was cyber-savvy and did not fall for the traps.

"There is guilt by association to be the one who wasn't attacked," Ms Hawkins said.

"It makes her look like an extension of the Kremlin's foreign policy."

The attack could also undermine Ms Le Pen's fiercely independent, nationalistic platform by suggesting she is too close to a foreign power.

This Sunday night Australian time, Mr Macron will go head-to-head with Ms Le Pen in the final round of the election to decide who will lead France into an increasingly uncertain time in Europe.

And if the US example is any guide and Ms Le Pen wins in a Trump-style upset, months from now the French people may also be wondering just how much hand Mr Putin had in the outcome.