In 2010, as part of what has been dubbed as Operation Aurora, Chinese hackers infiltrated a special database within Google's systems and gained access to a sensitive database worth of information about American surveillance targets.
Google reported the hack publicly years ago, saying that the sophisticated attack resulted in the theft of Google intellectual property and the partial compromise of some human rights activists' email accounts.
When the news first surfaced in 2010, Google said hackers stole the source code behind its search engine, and targeted email accounts of activists critical of China's human rights record. But recently discovered that the hackers also obtained surveillance information, including emails belonging to suspected spies, diplomats and terrorists which law enforcement officials had been monitoring. Google reported this breach to the FBI, resulting in a national security investigation.
According to the sources, hackers were after the names of Chinese intelligence operatives who were the target of American surveillance. The extent of the compromise is not known. An FBI investigation did not uncover any evidence that the information had been used to hurt national security, and Google tightened its defenses in the aftermath.
Last month, a senior Microsoft official suggested Chinese hackers had targeted the company's servers about the same time Google's system was compromised. The official said Microsoft concluded that whoever was behind the breach was seeking to identify accounts that had been tagged for surveillance by US national security and law enforcement agencies.
The Operation Aurora attacks reportedly targeted at least 34 companies, including Adobe, Juniper, Rackspace, Symantec, Northrop Grumman, Morgan Stanley and Yahoo.