“These attacks and the surveillance they have uncovered -- combined with the attempts over the past year to further limit free speech on the web -- have led us to conclude that we should review the feasibility of our business operations in China,” David Drummond, Google's chief legal officer, wrote in the post.

In mid-December the company detected a “highly sophisticated and targeted attack” coming from China on its infrastructure that resulted in some of its intellectual property being stolen, Drummond wrote. He didn't disclose exactly what had been stolen.

Google later discovered it was not the only company targeted. “As part of our investigation we have discovered that at least twenty other large companies from a wide range of businesses -- including the Internet, finance, technology, media and chemical sectors -- have been similarly targeted,” Drummond said.

Google said it is in the process of notifying those companies and also working with U.S. authorities.

In addition, it found that the primary goal of the attacker seemed to be accessing Gmail accounts of Chinese human rights activists. Drummond said only two Gmail accounts were accessed, and that only account information and not the content of e-mails was accessed.