Although initial attacks were launched using malicious Word attachments, hackers later expanded the campaign to include malformed Excel files, according to Mila Parkour, the independent security researcher who reported the Flash flaw to Adobe.

Parkour, who has been tracking the attacks for more than a week, has published information about them on her blog.

Some of the earliest messages in the attack tried to get recipients to open the attached Word or Excel files by claiming they offered information on China's antitrust laws, or a purported Japanese nuclear weapons program. Later messages were more mundane, and posed as corporate reorganization plans or new company contact lists.

Parkour also traced the resulting malware's "phone-home" communications to a server registered in China, and noted that some of the malicious Word and Excel documents had been originally crafted in Chinese.

-- which includes a copy of Flash Player -- Thursday, fixing not only the Adobe bug but a trio of critical vulnerabilities in the browser's hardware acceleration technology. Like Internet Explorer and Firefox, Chrome taps the computer's graphics processor (GPU) to handle some page composition and rendering tasks.