And last night, just an hour before the end of official campaigning, thousands of documents including emails and accounts belonging to his En Marche! (On the Move!) movement were dumped online.
"It's just incredible what's happening," said Belgian researcher Nicolas Vanderbiest, a specialist on online rumours, whose map showing how the "Macron Leak" propagated on Twitter has Wikileaks at the centre.
Also Read
It says it stored its information in multiple-partitioned cells, with databases separated like fortresses, accessible by passwords that were complex and regularly changed.
But a squad of shadowy hackers seem to have found the back door.
"In this kind of organisation the real potential faultline is the human element," the head of computer services for En Marche! recently told AFP, requesting anonymity.
Because security procedures can become long and cumbersome, some people can be tempted to get around them by using personal email services which are little or badly protected.
On April 25, a report by Japanese cyber-security company Trend Micro, blamed a so-called "phishing" attack targetting the Macron campaign on Russian hacking group Pawn Storm, also known as Fancy Bears, Tsar Team and APT28.
The group, suspected of close links to the Russian security services, is also accused of having targetted the Democratic Party during last year's US presidential election, in which Republican-backed Donald Trump defeated Democrat Hillary Clinton.
In this kind of attack, which does not require sophisticated resources, hackers can open up security gaps in software, for example during an update or through a so-called mirror site.
This would be something like "en-nnarche.Com", hoping that a user when reading quickly would mistake the "nn" for an "m" and fall into the trap, revealing access codes.
The principle of phishing, a classic arm in the hackers' arsenal, is to send a large number of fake emails often containing infected attachments, hoping that a distracted recipient will click on one, creating a breach in the targetted system.
The gap is unlikely to show up immediately, and the loophole it generates may be exploited weeks or months later.
You’ve reached your limit of {{free_limit}} free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Exclusive premium stories online
Over 30 premium stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app
)