Five recent cases of cyberespionage upon crucial governmental, infrastructure or political systems:

— On Tuesday, the Wall Street Journal reported that unknown cyber-intruders had over the past two years hacked into defense-contractor servers housing information about the F-35, or Joint Strike Fighter, the next-generation fighter/bomber for the U.S., Britain and seven other close allies.

The hackers, whom all signs indicated were based in China, weren't able to get the most sensitive information because it's kept offline, but they did copy "several terabytes" — several thousand gigabytes — of data about the F-35's systems, internal maintenance and electronics.

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— In early April, unnamed government officials told the Wall Street Journal that cyberspies from China and Russia had broken into computer systems used by companies maintaining the three North American electrical grids.

Even worse, the spies had left behind software that could be used to disrupt the grids or take control of nuclear power plants. Chinese and Russian officials denied their governments were involved.

— Canadian researchers revealed in late March that a cyber-spy network based in China had broken into diplomatic computer systems involving 103 different countries. Beijing denied any official involvement, but the investigation had begun when the Dalai Lama, Tibet's leader-in-exile, noticed that sensitive documents from his own PCs had turned up in Chinese hands.

In another incident related to the spy network, a reporter who'd been e-mailing Tibetan exiles was warned off the case only hours later by Chinese officials.

— Just after Barack Obama's election victory in November, Newsweek revealed that both the Illinois senator's campaign and that of his rival, Sen. John McCain, had been spied upon by a foreign power that had placed spyware on staffers' computers.

The FBI and Secret Service contacted both campaigns over the summer with the news that either the Chinese or Russians had copied substantial amounts of information related to foreign policy; the McCain and Obama organizations quickly implemented security measures.

— For more than a year in 2001 and 2002, British hacker Gary McKinnon broke into nearly 100 U.S. military and NASA computers, purportedly seeking information about UFOs. The U.S. eventually figured out who he was and referred the case to Britain, where local authorities arrested him in 2002 but decided not to charge him.

The U.S. indicted him later that year and began extradition proceedings in 2005, which McKinnon has been fighting ever since. U.S. officials say McKinnon caused $700,000 worth of damages and deserves up to 70 years in prison; in Britain, he's become a cause celebre, with a recent diagnosis of Asperger's syndrome further compounding his victim status.