Francois Baroin, the French finance minister, confirmed a report in Paris Match that claimed the attack was unprecedented and affected around 150 of the ministry's 170,000 computer systems.
"We noted that a certain amount of the information was redirected to Chinese sites," an anonymous official is quoted as telling Paris Match, adding "that [in itself] does not say very much."
Reporting on the affair, the BBC newswire says that a complaint has been filed through the French courts, and that the French secret service, the DGSE, have been investigating.
"The perpetrators were a number of professional, determined and persistent hackers, according to Patrick Pailloux, director general of the French National Agency for IT Security, who confirmed that they had obtained sensitive information", says the BBC.
The Softpedia newswire, meanwhile, says that the attacks have been traced back to China, but adds that the case for Chinese hackers remains unproven.
"On the other hand, a Chinese cyber espionage effort cannot be ruled out either because, despite the government's repeated denials of involvement in such activities, other intelligence agencies have confirmed it uses such methods", noted Lucian Constantin of the newswire.
Mike Darvill, director of trusted security firm AEP Networks said that it comes as no surprise that the G20 became the target of cyber-attack. Sustained targeted cyber-attacks, he explained.
"Often designed to sneak access to sensitive files, the cyber perpetrators are often professionals seeking access to specific pieces of information", he said.
"All Government departments and every private contractor that protects high profile events or infrastructure must be made to adhere to the highest levels of security" he added.
"Without a scaled-up approach to cyber defence, national security is left open to compromise and sensitive information is at the mercy of those who have the technical knowledge to launch these targeted attacks."