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Comment Icon0 Chinese netizens seemed to be aware that the authorities were using keyword filtering in their quest to block potentially sensitive information from being disseminated online. Despite this grassroots knowledge, the vague and broad Internet laws in China rendered these keywords hidden from the public eye. It was not until August 2004 that Chinese hackers discovered a list of 987 sensitive keywords (in both Chinese and English) in a component of the popular Tencent QQ instant messaging. Launched in 1999, QQ boasts of around 160 million active users, 7.3 million paid subscribers and more than 13 million registered SMS users. Tencent is Asia’s number one and the world’s third most popular IM service provider (India Times, May 2007). Since there would be more than six million users online using QQ at the same time, it would have been technically difficult to use keyword filtering at the server end. Instead, Tencent slipped in a filtering program file at the client end (QQ2003 software). Chinese hackers found a dynamic link library, specifically the COMToolKit.dll file bundled with the QQ software, containing a list of keywords in both Chinese and English that were filtered by the software.


Figure 12: Categories of censored words hidden within QQ instant messenger (Bambauer et al., 2005)

Comment Icon0 As seen in Figure 12, the hidden list contained keywords categorized into obscenities, Falungong, Chinese officials, political terms, national minorities and banned dissident media. Hackers publicized this list by sharing it on a Chinese bulletin board system in August 2004 (Bambauer et al., 2005). Upon content analysis, about 15% of the words were sex-related, while the rest were all related to politics. About 20% of the words were Falungong-related, 15% were names of current officials and their relatives, about 10% were liberal political terminologies such as “democracy”, “freedom” and “dictatorship”, and about 5% were related to certain nationalistic issues, such as “defend Diaoyu Island”. About 15% of the forbidden words were related to anti-corruption, such as “smuggling”. The remaining censored words included names of dissidents, writers and intellectuals, and names of certain foreign publications (Xiao, 2004a). The discovery of this sensitive keyword list is far-reaching, as researchers are now able to test filtering on websites, BBS and text-messaging services.

Comment Icon0 The filtering of keywords over instant messengers was not limited to the QQ2003 software. In October 2008, the Information Warfare Monitor (IWM) published insurmountable evidence that the popular TOM-Skype VoIP client was not only blocking keywords from chat messages, but also monitoring and reporting the contents of Skype users’ private text conversations. To understand the motivation for surveillance on Skype users, China has the largest number of Voice-over Internet Protocol (VoIP) users in the world, with 42 million registered users on TOM’s compromised client as of June 2007 (“Skype has over 25m users in China,” 2006). There were two key factors for the national popularity of TOM-Skype. First, VoIP was popular because it allowed users to call one another relatively cheaply or even free over the Internet. As an additional feature, the Skype client has instant-messaging features as well. Secondly, TOM-Skype was granted a monopoly over VoIP paid service (marketed as SkypeOut) for at least two years by the Chinese government (Maitlin, 2006). Following this, only China Netcom and China Telecom were permitted to offer pilot commercial VoIP services in selected cities (“China to issue its first VoIP license,” 2006).

Comment Icon0 This breach of trust violated Skype’s previous assurance that “full end-to-end security is preserved and there is no compromise of people’s privacy”, even on the customized Chinese client. Using the Chinese Skype client distributed by the Chinese portal company TOM Online, IWM researcher showed that when these keywords were mentioned in conversations, the client software also sent an encrypted message to one of eight remote servers hosted in China. Through poor security in these servers, it was discovered that the TOM-Skype clients sent extensive logs on user activities, including archives of more than 166,000 censored messages from 44,000 users. Skype’s parent company had since denied involvement in TOM’s modifications to their core client software, although they were aware that TOM had introduced censorship filters into the Chinese Skype client.

Chapter 6.1.5 – Filtering Instant Messages

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