France's finance ministry was subject to a cyber attack in December targeting information related to its presidency of the Group of 20 nations, officials said on Monday.
Budget Minister Francois Baroin said the infiltration of some 150 computers did not seek access to any personal records or tax information contained in the ministry's computers.
What was targeted, it seems, was the organization of the G20, Baroin, who is also the government's spokesman, told Europe 1 radio.
The minister said officials had been shocked by the scale of the attack: It is probably the first time it has been so spectacular.
He added that there were some clues over the identity of the hackers, but he did not provide further details.
However, the head of France's national computer security agency Patrick Pailloux said that the attackers were professionals, determined and organized.
This attack was not carried out with three computers in a garage, he told a news conference.
France began its G20 presidency in November with ambitious plans to tackle high commodities prices, reform the global monetary system and complete the G20's framework for tackling the global economic imbalances caused by some countries' large trade surpluses or government deficits.
It hosted a meeting of G20 finance ministers and central bank governors in the finance ministry last month, which agreed on a list of indicators to measure imbalances in the global economy, including trade balances and government deficits despite strong resistance from China.
Beijing managed to exclude real interest rates and levels of international reserves from the list and G20 nations must now establish guidelines by April for using the list.
Finance Minister Christine Lagarde said officials reacted quickly to the cyber attack.
Once we identified the problem, measures were immediately taken, especially for documents related to the G20 since we realized very quickly that they were apparently of interest, she told journalists, noting that Canada was also recently targeted by cyber attacks.
A source close to the minister said that the ministry's security services had finished securing the system last weekend after detecting the attacks in December, adding that some 10,000 computers in the ministry had been protected.
He could not confirm a report on the Web site of Paris Match (www.parismatch.com) that some of the information had been redirected toward Chinese Web sites.