In recent weeks, China stands accused not only of the Pentagon attack, but also of daily striking German federal ministries and British government offices, including Parliament. After an investigation in May, officials at Germany's Office of the Protection of the Constitution told Der Speigel that 60 percent of all cyberattacks on German systems come from China. Most originate in the cities of Lanzhou and Beijing, and in Guangdong Province, centers of high-tech military operations.
German Chancellor Angela Merkel publicly raised the issue with Chinese Premier Wen Jiabao in Beijing last month. Mr. Wen did not deny China's activity, but said it should stop. President George Bush, prior to his meeting with Chinese President Hu Jintao in Sydney, Australia, at the APEC summit last week, stated that respect of computer "systems" is "what we expect from people with whom we trade."
The accusations, hard to prove conclusively, still illumine an emerging theater of low-level attacks among nations. This spring, presumed Russian hackers made headlines with a one-off cyberblitz of Estonia, shutting down one of the most wired countries in Europe for a week – blunt payback for removal of a Soviet war memorial.
But China's cyberstrategy is deemed murkier and more widespread. The tenaciousness of Chinese hackers, whose skills were once derided by US cyberexperts, has begun to sink in to Western states and their intelligence services.
Probes of the Pentagon system that would bring US intervention should China attack Taiwan are part of a program dating to the 1990s that links cyberwarfare to real-world military action by China's People's Liberation Army. The very probe shows success in China's long-term program, experts say.
"The Chinese want to disrupt that unofficial network in a crucial time-frame inside a Taiwan scenario," says Mr. Mulvenon. "It is something they've written about. When you read what Chinese strategists say, it is the unclassified network they will go after … to delay deployment. China is developing tremendous capability."