Around 40 million users of the Tianya.cn online forum had their user name, passwords, email addresses, and other information posted online, according to a report by the Shanghai Daily newspaper. Tianya.cn is one of the largest online forums in China, with more than 60 million users.
The forum published an announcement saying that the security breach was caused by an outdated security measure widely used in 2009, which recorded all users' passwords in a database but did not encrypt them.
In response to the data breach, Tianya.cn posted a letter of apology on its homepage and sent emails to users in which it admitted that data pertaining to a portion of its user base had been leaked following a hacking attack.
The company reported the incident to the provincial and municipal Public Security Bureau authorities in Haikou, and the police have launched an investigation.
In addition, profiles of more than 50 million users of several Chinese microblogging sites were posed online, according to Shanghai Daily.
The Shanghai city government is requiring users of these services to register using their real names. The recent leaks have spread doubts among users about the wisdom of the real name policy, which has been adopted in other major Chinese cities, including Beijing, the newspaper said.