Hackers have infiltrated over 150 computers in the French finance ministry in an attempt to steal documents relating to the country's presidency of the G20 Summit in February, according to reports.
In another indication of the growing cyber threat to sovereign nations, hackers also tried to attack other ministries.
Although members of the ANSSI (National Security Agency for Information Systems) have been working on the case for months, the full extent of the attacks may still not be known.
Pailloux Patrick, executive director of ANSSI, told Paris Match, which first broke the story, that "this is the first attack against the French state and of this magnitude at this scale".
The attacks apparently began around December 2010, and arrived in the form of email attachments loaded with Trojan malware.
Most of the 150 officials targeted worked on the G20 summit, and the Canadian finance ministry, which hosted the G20 before France, was also hacked in a similar way at the same time.
Although there is no firm evidence yet, some commentators have implicated China in the attack, given that a key point on the G20 summit agenda was trade imbalances - an important topic for China, which was accused of deliberately undervaluing its yuan currency.
In addition, a senior official was quoted by Paris Match as saying that "a certain amount of information was redirected to sites in China, but this does not say much".
However, Graham Cluley, senior security consultant at Sophos, warned that it is too early to be blaming China, arguing that the exact location of the hackers can be obfuscated by their ability to use compromised PCs to carry out their attacks.
"I think it's dangerous to conclude that a hack was state-endorsed unless there's definitive proof," he added in a blog post.
"We'd be naive to think that the Chinese (and just about every other country around the world) isn't using the internet for its political, commercial and military advantage, but we should be very cautious about making assumptions without having all the proof in front of us."
The UK government is no stranger to cyber espionage, and several senior figures have publically admitted over the past year that key systems have been infiltrated.
Most recently, foreign secretary William Hague told the Munich Security Conference last month that some of his staff were targeted by criminals who managed to infect systems with the Zeus information stealing Trojan.
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