The hugely influential New York Times newspaper has said its computer system has been systematically hacked from China over the past four months.
After the NYT's announcement the Wall Street Journal also said it had fallen victim to hackers from China trying to monitor its coverage of the country.
The NYT hacking followed the publication of an investigation into the financial affairs of Chinese Prime Minister Wen Jiabao.
All the paper's journalists had their passwords hacked and the evidence suggests the infiltrators specifically targeted reporters who had worked on the story of October 25 which found that relatives of Wen Jiabao had made billions of dollars in business deals.
Particular attention was paid to the email account of Shanghai bureau chief David Barboza.
Knowing that it could face "consequences" over its story, the paper had asked the huge AT&T communications company to monitor its systems for unusual activity.
This was spotted on the day the story was published. It worked to clear its system but, by November 7 with multiple spying viruses still inside, it brought in experts from a company called Mandiant to help.
The specialist company told them that the pattern of hacking began at 8am Beijing time and continued for normal Chinese working hours with occasional late shifts going on until midnight. It concluded that the type of attack suggested methods associated with the Chinese military.
In order to disguise themselves, the hackers routed their malware via American universities and then into the NYT system before installing 'remote access tools' which allow the installer to read every key stroke made on a computer.
The NYT, which has now published the inside story of the attack, took care to ensure China's right of reply and quoted a spokesman as saying: "Chinese laws prohibit any action including hacking that damages internet security."
One of the many interesting aspects to the attack is that, if true, China is now using its vast cyber army to try to control the country's image as well as for what are now becoming almost routine attacks on other countries' business and defence sectors.
Last year, the US government criticised China for its cyber warfare, but did not acknowledge that it, too, is busy developing cyber weapons. It is suspected that, several years ago, the US began work with the Israelis on a project which resulted in the sophisticated "Stuxnet" worm which attacked Iran's nuclear programme.
The Russian and Iranian defence sectors are thought to be giving a high priority to cyber warfare, and Britain's intelligence agencies have spoken openly about the need for the UK to develop capabilities to match its rivals.
The Foreign Office is thought to have been cyber attacked by China two years ago but, for security reasons, details have never been made public.
China has an advantage over most countries as this new type of warfare develops - its massive population. Cyber warfare is not just technical, it can also be labour intensive.
Given that China has 540 million internet users, linking to 700 million internet-connected devices, it has a capacity to attack which others lack. Those numbers also give it an advantage in defence.
If Luxembourg (population 500,000) had got into the NYT system, finding the source might be easy. If it is China (population 1.3 billion), it is more akin to looking for a digital drip in an electronic waterfall.