US analysts believe a Chinese freelance security consultant with government ties was the author of the code used in cyberattacks on Google and other companies, the Financial Times reported on Monday.
The Wall Street Journal reported meanwhile that a prominent Asian hacking group that is likely Chinese may have been the perpetrators of last year's attacks on the Internet giant and as many as 33 other companies.
The FT, citing an unidentified researcher working for the US government, said a Chinese security consultant in his 30s wrote the part of the program that used a previously unknown security hole in Microsoft's Internet Explorer Web browser to break into computers and insert spyware.
The newspaper said Chinese officials had special access to the work of the author, who posted pieces of the program to a hacking forum.
The man is not a full-time Chinese government worker and did not launch the attacks, the newspaper said, adding that he would "prefer not be used in such offensive efforts."
"If he wants to do the research he's good at, he has to toe the line now and again," the US analyst said. "He would rather not have uniformed guys looking over his shoulder, but there is no way anyone of his skill level can get away from that kind of thing.
"The state has privileged access to these researchers' work."
The FT also repeated claims made last week in The New York Times that the attacks had been traced to computers at Shanghai Jiaotong University and the Lanxiang Vocational School located in the eastern province of Shandong.
Both institutions have denied involvement, as have the Chinese authorities.
The Wall Street Journal said Monday that the group that attacked Google and others may have been involved in previous attacks tracked by intelligence and law-enforcement officials.
"It is the same folks that have been behind a hell of a lot of other attacks," the Journal quoted a person familiar with probes into some of the affected companies as saying.
The Journal said the group investigators are focusing on uses Chinese computer systems to mount its attacks and has a history of primarily attacking corporations -- not the US military or other government agencies.
The Journal said it is not clear whether the hackers have connections to the Chinese government or whether they are a "patriotic" hacking group that acts in the government's interests.
China has repeatedly denied involvement in the attacks, which have strained US ties and prompted Google to threaten to leave the country.
Google vowed in January to stop bowing to Web censors in China in the wake of the cyberattacks aimed at the US firm's source code and at Gmail accounts of Chinese human rights activists around the world.
Google continues to filter searches as per Chinese law while trying to negotiate a compromise with officials there.
US President Barack Obama said last month that he was "troubled" by the cyberattacks on Google and wants answers from China.
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