The United States has backed Google's decision to no longer support China's censoring of Internet searches and said the issue was of considerable economic importance as well as involving free information flow.

Washington again demanded an explanation from Beijing on the issue, the latest row to break out between two of the world's economic giants.

China has defended its censorship after Google threatened to shut down its Chinese-language website and offices in China following a spate of cyber-attacks last month.

It seems to me that the principles that Google is trying to uphold are not just important in a moral or rights framework, but are also of very considerable economic importance, senior White Senior White House economic adviser Lawrence Summers told reporters on Thursday.

He said that information flow is central as China's economy matures and transforms from an industrial-based economy to a more knowledge-based economy.

U.S. Deputy Assistant Secretary for East Asian and Pacific Affairs David Shear met a Chinese diplomat in Washington on Thursday to seek an explanation about the cyber-attacks and censorship, State Department spokesman P.J. Crowley said.

The incident raises questions about both Internet freedom and the security of the Internet in China, Crowley said.

We have serious concerns about this and its ramifications, and we're going to continue our dialogue with China on these and other kinds of issues, he said of Shear's meeting with China's deputy chief of mission in Washington.

There are ... business standards and expectations, international norms that you expect your business partners to live up to, added Crowley.

A senior U.S. official said Shear received no reply from the Chinese on the Google case.

China on Thursday brushed aside the hacking claims, telling companies not to buck state control of the Internet.

Most of the filters on Google.cn were still in place on Friday, though controls over some searches, including the June 4, 1989 Tiananmen crackdown, appear to have been loosened.

According to local laws, rules and policies, some search results cannot be shown, reads a message in Chinese at the bottom of searches for sensitive topics, a line Google.cn has been using even before the current case.

FLAW IN MICROSOFT

Security firm McAfee Inc said that the recent cyber-attacks on Google and other businesses exploited a previously unknown flaw in Microsoft Corp's Internet Explorer browser.

The weakness in the world's most widely used browser was identified by McAfee and later confirmed by Microsoft.

Google said on Tuesday that in mid-December, it detected an attack on its corporate infrastructure originating from China that resulted in the theft of its intellectual property. It eventually found that more than 20 other companies had been infiltrated.

McAfee said on Thursday that those who engineered the attacks tricked employees of the companies into clicking on a link to a website that secretly downloaded sophisticated malicious software onto their PCs through a campaign that the hackers apparently dubbed Operation Aurora.

We have never seen attacks of this sophistication in the commercial space. We have previously only seen them in the government space, said Dmitri Alperovitch, a vice-president of research with McAfee.

Microsoft later sent out an advisory to help users mitigate the problem. It is still working on a patch that would solve it.

The company has determined that Internet Explorer was one of the vectors used in targeted and sophisticated attacks against Google and other corporate networks, Microsoft said.

The world's largest software company said using Internet Explorer in protected mode with security settings at high would limit the impact of the vulnerability.

We need to take all cyber-attacks, not just this one, seriously, said Microsoft Chief Executive Steve Ballmer in an interview on CNBC. We have a whole team of people that responds in very real time to any report that it may have something to do with our software, which we don't know yet.

(Additional reporting by Jeff Mason and Paul Eckert in Washington and Jim Finkle and Bill Rigby in Boston; Editing by Benjamin Kang Lim and Raju Gopalakrishnan)

Hacking Google China