The patch, due out on Thursday, "addresses the vulnerability related to recent attacks against Google and a small subset of corporations," said Jerry Bryant, senior security program manager at Microsoft. "Once applied, customers are protected against the known attacks that have been widely publicized."

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Google said last week it had been the target of sophisticated cyber-attacks in China, along with more than 20 other companies. Microsoft acknowledged that the hackers took advantage of a weakness in Internet Explorer 6 to mount the attacks.

Microsoft said it continues to see some attacks, with the only successful attacks against Internet Explorer 6. The most recent version of the software is Internet Explorer 8.

(Reporting by Bill Rigby, editing by Leslie Gevirtz)