As China's 500 million Internet users rapidly adopt social media, academics and entrepreneurs are figuring out ways to track online messages and blog posts to better understand what the government censors...China's government employs software and an army of thousands to police the Internet, but it leaves much of the censoring to social-media sites like Sina Corp. to take down posts that violate...rules... While it is generally known that certain words or phrases...will trip the censors, the scope isn't fully understood. These sites usually offer clues that they deleted a post due to censorship...That is helping researchers figure out how China's opaque power structures work...Hong Kong University developed software called WeiboScope, which scans posts from Sina Corp.'s Weibo...analyzing censorship trends...