Functional defects Jinhui claimed that Green Dam recognized pornographic images by analyzing skin-coloured regions, complemented by
human face recognition. However, according to a
Southern Weekly article, the software is incapable of recognizing pictures of nudity featuring black- or red-skinned characters but sensitive enough to images with large patches of yellow that it censors promotional images of the film
Garfield: A Tail of Two Kitties. The article also cited an expert saying that the software's misrecognition of "inappropriate contents" in applications including
Microsoft Word can lead it to forcefully close those applications without notifying the user, thus cause data losses. On 21 June 2009,
Ming Pao reported that the software detected and censored pictures of Chinese political leaders as pornography. On 11 June 2009, a
BBC News article reported that potential faults in the software could lead to a large-scale disaster. The report included comments by
Isaac Mao, who said that there were "a series of software flaws", including the unencrypted communications between the software and the company's servers, which could allow hackers access to people's private data or place malicious script on machines on the network to "affect [a] large scale disaster". The software runs only on
Microsoft Windows x86, so
Microsoft Windows x86-64,
Mac OS X,
Linux and users of other operating systems are ignored. Also on 11 June 2009, a
Netease article reported that the master password of the software could be easily cracked. The software stores the
MD5 checksum of the password in a
text file disguised as a
DLL (C:\Windows\System32\kwpwf.dll), thus the password can be arbitrarily set by changing the contents of the file. This was ridiculed by some
netizens as the software being crackable by "elementary school students". Researchers from
University of Michigan found the uninstaller "appears to effectively remove Green Dam from the computer," whereas some sources state that part of the software (e.g. executables loaded on startup) cannot be removed by its own uninstaller, but that most of it (per either blogs or media reports) was removed according to the PRC government's request.
Security vulnerabilities On 11 June 2009, Scott Wolchok, Randy Yao, and
J. Alex Halderman from the
University of Michigan published an analysis of Green Dam Youth Escort. They located various
security vulnerabilities that can allow "malicious sites to steal private data, send spam, or enlist the computer in a
botnet" and "the software makers or others to install malicious code during the update process". They recommended that users uninstall the software immediately for protection. Wolchok
et al. indicated the existence of
buffer overflow vulnerabilities which they ascribed to programming errors. Buffer overflow may occur when the software performs
URL filtering or updates its blacklist filter files due to the use of fixed-length buffers, and can corrupt the
execution stack and potentially allow execution of malicious code. Furthermore, the feature of automatic filter update opens the door to the computer being remotely controlled by the software's makers and possibly third parties who manage to impersonate the update server because the updates are delivered via unencrypted
HTTP.
Alleged software plagiarism and license violation In addition to security vulnerabilities, Wolchok, Yao and Halderman also found that a number of blacklist files used by Green Dam Youth Escort were taken from the censorship program
CyberSitter, from
Solid Oak Software Inc. The decrypted
configuration file references blacklists with download URLs at CyberSitter's website. They also discovered in the software a news bulletin published by CyberSitter in 2004, whose inclusion was conjectured by them to be accidental. Both the Wolchok
et al. report and a technical analysis released on
WikiLeaks indicated that software contains code libraries and a configuration file from the
BSD-licensed computer vision library
OpenCV. Internet lawyer
Jonathan Zittrain said that if the computers are only sold in China it would not be a violation of U.S. copyright and the issue "would have to be resolved in a Chinese court under Chinese law". In January 2010, Cybersitter filed a $2.2 billion lawsuit against the PRC government and Jinhui Computer System Engineering charging that Green Dam Youth's developers had stolen more than 5,000 lines of code from Cybersitter. In December 2010, a California court denied a motion to have the suit dropped. The motion was filed by
Sony,
Acer, BenQ and Asustek, who were named as defendants in a list that also includes Chinese PC makers
Lenovo and
Haier.
Reactions of the software's makers According to an addendum to the Wolchok
et al. report published on 18 June 2009, makers of Green Dam Youth Escort silently patched the software on 13 June, addressing at least the one particular buffer overflow vulnerability showcased in the original report. In spite of the patch, the software nevertheless remained vulnerable to more sophisticated attacks, as demonstrated by a new example attack page included in the addendum, leading the authors to stand by their previous recommendation that users uninstall the software immediately. In 2010, other commentators, whilst noting no change in the government's policy towards policing the Internet, said the de facto abandonment of the project was an admission of error. == See also ==