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Figure 14: Green Dam Youth Escort on Microsoft Windows. (Wolchok, Yao, & Halderman, 2009).

Comment Icon0 While most technological forms of information regulation on the Internet have been controlled via computer networks, the Chinese Communist Party’s latest efforts are focused on the end users themselves, specifically their personal computers. Developed by Zhengzhou Jinhui Computer System Engineering Ltd, with counsel from Beijing Dazheng Human Langauge Technology Academy, the Green Dam Youth Escort (绿坝·花季护航 in simplified Chinese) is a content-filtering software specifically aimed at blocking access to forbidden sites all related to online pornography (Watts, 2009). Designed to work on Microsoft Windows operating system (Figure 14), the Green Dam Youth Escort software automatically updates itself by downloading the latest list of prohibited sites from an online database. Operating systems such as Mac OSX as well as Linux are excluded from the Green Dam installation mandate. Bryan Zhang, the founder of Jinhui, said that users would not be permitted to see the list, but would have the option of unblocking sites and uninstalling the software (Figure 15). Additional search terms can also be blocked at the owner’s discretion (Watts, 2009).

Figure 15: Green Dam website-filtering configuration screen (Wolchok, Yao, & Halderman, 2009).

Comment Icon0 The Green Dam Youth Escort project began as early as 2008, when the Ministry of Industry and Information Technology (MIIT) was instructed by political leaders to implement a community-oriented Internet-filtering software project. With the support of the Central Civilisation Office and the Ministry of Finance, the project’s aim was to build a “green, healthy network environment, to protect the healthy growth of young people” (MIIT, 2008). By October 2008, the ministry negotiated with the software suppliers and 50 web portals to make the software publicly available without charge. From the trials in Zhengzhou, Nanjing, Lanzhou and Xi’an, more than 2,000 installations took place. By December 2008, the trials included 10 more cities, including Chengdu, Shenyang, Harbin and Qingdao, where the software saw more than 100,000 downloads. By March 2009, the software registered three million downloads, due partly to the participation of China’s five leading PC vendors Founder, Lenovo, Tongfang, Great Wall and HEDY (MacKinnon, 2009b).

Comment Icon0 After sufficient trials were conducted, the Ministry of Industry and Information Technology (MIIT) issued a directive on 19 May 2009, stating that the following actions would be mandatory by 1 July 2009: 1) Computer manufacturers have to ship machines bound for China with the software pre-installed; 2) allow users to re-install the software by including it on a compact disc or in a partition of the hard drive; and 3) manufacturers are required to report the number of machines shipped with the software to the government (MIIT, 2009). Interestingly, the government’s mandate did not require end-users to run the software, which meant that they could choose not to install or even uninstall the Green Dam software if they wanted to (Watts, 2009).

Comment Icon0 To assess the potential impact of the Green Dam filtering software, a team of computer science researchers at the University of Michigan examined the software’s capabilities as well as security vulnerabilities (Wolchok, Yao, & Halderman, 2009). They confirmed that the software filters content by blocking website URLs, online images and monitoring text across applications. To filter website URLs, Green Dam uses patterns contained in whitelist and blacklist files (*fil.dat, adwapp.dat and TrustUrl.dat). To filter images containing nudity, Green Dam includes computer vision technology which reportedly works by flagging images containing large areas of human skin tone, while making an exception for close-up of faces. This technique is not always effective, as the software has been known to falsely block images of pink-colored pigs as well. Finally, the text-filtering feature scans text-entry fields in various applications for blocked words, including obscenities and politically-sensitive phrases (e.g., Falungong). Researchers determined that the blacklisted terms were contained in three files, which upon decryption yielded three files, namely xwordl.dat, xwordm.dat and xwordh.dat. When Green Dam detects keywords in these files, the offending program is forcibly closed and an error image is displayed (Figure 16).

Figure 16: Green Dam error message when encountering prohibited content online. (Wolchok, Yao, & Halderman, 2009).

Comment Icon0 Interestingly, researchers at the University of Michigan discovered several serious complications with the Green Dam software, including how it had web-filtering vulnerability, blacklist-update vulnerability and illegally copied computer code from American-made filtering program Cybersitter. As a flaw in the web-filtering code, the researchers were able to demonstrate how an actual attacker could use malicious code to exploit this weakness, thereby crashing the users’ web browsers. Turning to the blacklist-update vulnerability, the researchers determined that the software allowed Green Dam developers, or third-party impersonators, to execute arbitrary code and install malicious software on the users’ computers after installing a filter update (Wolchok, Yao, & Halderman, 2009). In the most extreme case, attackers could take control of the users’ computers using this method. Finally, researchers also found that the filtering blacklist contained both political and pornographic content, with some of the keywords apparently copied from an American filtering software, Cybersitter. This was confirmed by Solid Oak, which found pieces of its Cybersitter computer program in the Green Dam Youth Escort software. To date, Bryan Zhang of Jinhui Computer System Engineering Inc. has denied that his company had stolen the programming code (Shiels, 2009). Since the time of publication, the Green Dam software has been repeatedly and quietly patched, though researchers have found that it still contains vulnerabilities.

Comment Icon0 On 30 June 2009, the Ministry of Industry and Information Technology (MIIT) unexpectedly announced that the Green Dam Youth Escort software mandate would be delayed indefinitely, claiming that some computer manufacturers needed more time (Xinhua News, June 2009). However, the government could have simply been pressured by criticisms on Green Dam’s security vulnerabilities and privacy encroachment. The impact of China’s Green Dam software mandate sent discontent beyond mainland China. Ed Black, president of the Computer and Communications Industry Association (CCIA), criticised the move, saying that the Chinese were attempting to “not only control their own citizens’ access to the Internet but to force everybody into being complicit and participate in a level of censorship” (Moses, 2009). Possibly as a politically motivated strategy to forge closer ties, Taiwanese manufacturers Acer, Asus and BenQ announced that they were already shipping products with Green Dam. Sony and Lenovo joined them later (Ross, 2009). It has been estimated that in the next two years, China’s PC market will be the world’s largest with 50 million units shipped annually by 2012 (Shiels, 2009).

Comment Icon0 Online surveys conducted by some of China’s most popular web portals like Sina and Netease showed that four out of five netizens will not use the Green Dam software or have it installed. On Tencent, over 70% of poll participants said it was unnecessary for new computers to be preloaded with filtering software. On Sohu, over 70% of poll participants said filtering software would not effectively prevent minors from browsing inappropriate websites (, 2009). As an Internet satire, Internet citizens have even created manga-style ‘Green Dam Girl’ dressed in green, wearing a river crab hat, holding a rabbit (the Green Dam mascot) in hand, and armed with a paintbrush to wipe out online filth (Figure 17).

Figure 17: One of the variations of the Green Dam Girl (, 2009).

Comment Icon0 While China periodically launches campaigns against online pornography, the Chinese Communist Party’s Green Dam Youth Escort mandate is a way in which the government creeps ever closer into the home of every Chinese netizen. Professor Jonathan Zittrain of Harvard’s Berkman Center noted that “[o]nce you’ve got government-mandated software installed in each machine, the software has the keys to the kingdom [...]. While the justification may be pitched as protecting children and mostly concerning pornography, once the architecture is set up it can be used for broader purposes, such as the filtering of political ideas” (Fildes, 2009). The fact that Green Dam’s blacklist contains both political and pornographic keywords demonstrates the true intention of the Chinese government in mandating software pre-installations (Wolchok, Yao, & Halderman, 2009).

Chapter 6.2 – Green Dam Youth Escort Software


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