K-12 学校计算机网络/第 9 章

安全基础

	Technology of Filtering Programs: Blocking Child Pornography on the Internet 

布莱恩·阿普特

Child pornography.  The Internet, a prime source of free, unfettered information, leaves it vulnerable to child pornography, a very small part of what’s available on the Internet that is not readily in public view. Erotic and pornographic information, available on the Internet virtually to everyone, including children, has created a great deal of concern. Because some 20% of children (1 in 5) aged 10 to 17 have been sexually solicited over the Internet, efforts have been made to block child pornography, including the Child Online Protection Act (COPA) (1998) that had been passed and, then, struck down as unconstitutional, most recently July 22 by the U.S. Circuit Court of Appeals in Philadelphia. The federal appeals court, in its ruling, argued that COPA is overly broad and vague and violates the First Amendment because “filtering technologies and other parental control tools offer a less restrictive way to protect children from inappropriate content online.” (Tessler, J., A.P., July 23, 2008, 3A)
What is child pornography?  Child pornography consists of photographs, videotapes, magazines, books, and films that depict children in sexual acts. It is illegal. Although law enforcement has begun to police the Internet, it still relies principally on a vigilant watch of cyberspace to apprehend lawbreakers and on the technology of filtering to block or screen pornography from children using the Internet. 
  But not only schools and families! Businesses are also concerned with the type of Internet materials their workers are assessing over corporate networks. Most companies simply don’t want their workers accessing that material on company time. Some companies now lease the same software parents and schools are buying, and it checks all incoming Internet traffic to every computer in the company on a vigilant watch of cyberspace to apprehend lawbreakers. 

工作场所监控方法：许多公司使用“数据包嗅探器”来跟踪员工的互联网行为，这种软件会检查或“嗅探”网络上传输的每个数据包，并将它们存储在日志文件中。过滤的“嗅探器”只捕获从指定网站进入网络的数据包。这使技术支持人员能够检查文件并重建互联网行为。一种更隐蔽的软件，称为键盘记录器，会在员工不知情的情况下安装在他们的电脑上。这种软件会记录每次按键，并将其记录下来。儿童互联网保护法 (CIPA) 及其过滤扩展。CIPA 要求接受普遍服务折扣 (USD) 的接收者和接受 ESEA 第三章或图书馆服务资金的接收者必须拥有技术来过滤儿童色情内容和对未成年人有害的材料。然而，地方官员有权为了研究或其他合法目的暂时暂停过滤或屏蔽。互联网过滤技术：然而，比立法行动更有效的，是互联网过滤技术——一种软件，可以让父母和老师确保他们的孩子不会浏览色情内容。一些公司，如 Net Nanny、SurfWatch 和 CyberPatrol，制造和销售保护软件，可以监控他们在互联网上的时间。这些软件功能强大，易于安装，可以帮助父母保护孩子。该软件会检查网站内容，并禁止孩子访问不适合他们的网站。一些广泛用于家庭网络的路由器具有过滤功能，可以屏蔽色情内容、仇恨网站、可疑聊天室和其他互联网危险。此外，它们与 Google、Yahoo、Alta Vista、Dogpile、Lycos、AllTheWeb 和 MSN 等广泛使用的搜索引擎中提供的“安全搜索”选项合作。当孩子们在万维网上使用搜索引擎进行“仅图片”搜索时，他们不会看到指向屏蔽网站的链接，这些网站提供针对色情图片的保护。过滤可以以多种方式实现：过滤服务。像 AOL 和 MSN 这样“对儿童友好的”互联网服务提供商，为他们的客户提供有效的过滤服务。过滤软件。一些软件程序会监控互联网使用情况，并阻止万维网以及像对等下载网络、聊天室、即时消息、FTP、论坛和电子邮件等鲜为人知但同样危险的区域中的令人反感网站。去年夏天（2007 年 7 月）出现了一项打击儿童色情内容的新战线。Verizon 和 Time Warner Cable 是美国最大的两家服务提供商，它们为大约 1600 万用户提供服务。此前，纽约州的卧底探员发现互联网提供商允许儿童色情内容在网上泛滥（但在抵抗和长时间谈判之后），它们同意限制对儿童色情内容的访问，并从服务器中删除传播儿童色情内容的互联网公告板和网站。他们进一步同意删除托管在三家公司服务器上的贩卖儿童色情内容的网站。

  New York State developed a new system for identifying child pornography online. Every online picture has a unique “Hash Value” that, once identified and collated, can be used to digitally match the same image wherever it is distributed. By building a library of the Hash values for images identified as child pornography, investigators are able to filter through tens of thousands of online filters at a time, speedily identifying which Internet Service Providers (ISPs) are providing access to child pornography. Investigators, by pursuing Internet service providers, essentially moved beyond the traditional enforcement strategy of confronting the producers of child pornography and their customers. Spearheaded by the National Center for Missing and Exploited Children, these major Internet service providers represent a significant new front on the battle against child pornography.
   Many in the communication industry, arguing that, given the decentralized and largely unmonitored nature of the Internet, they could not be responsible for content online, had previously resisted similar efforts.  But not only that! These companies, plus Sprint, agreed to shut down access to traffic in pornographic images of children on Usenet, one of the oldest outposts of the Internet that, some thirty years ago, was one of the earliest sources of information online. As the World Wide Web continued to flourish, Usenet, essentially supplanted by other search agents, became a favored back alley for traffickers in illicit material. 
  For all of the apparent progress of filtering campaigns against Internet pornography, extended by the goal of making it extremely difficult to find or disseminate pornography online, it is acknowledged that access can not be eliminated entirely. Potential obstacles include third-party companies that sell paid subscriptions that permit consumers to access newsgroups privately, thus preventing even their Internet service providers from tracking their activity. 
  However, for all of its limitations, the process of filtering to prevent child pornography on the Internet has had significant success. For while Internet usage skyrocketed, crimes against children notable declined during the last ten years.

网站限制。有些浏览器可以检查网站中嵌入的特殊评级标签。有关这些标签的信息，请参见互联网内容评级协会 (ICRA) www.icra.org。这些标签通常标识一个网站或一个特定页面的内容描述符。用户可以将浏览器设置为显示“幻想暴力”但不显示性内容的页面。嵌入评级标签的网站不会显示，因为浏览器无法确保该网站是安全的。这种评级标签系统并没有得到广泛使用，可能有用，但到目前为止，似乎还不是解决互联网上儿童色情内容问题的普遍解决方案。如何判断网站是否适合？首先，在内容进入系统时过滤传入内容。过滤器被编程为查找可能包含“太多肉色”的目标词语或图像。然而，这种过滤器无法消除有关性教育或乳腺癌的网站。（特里尔，2006 年）此外，虽然过滤器会查找包含目标词语的电子邮件，但它可能无法识别“s*e*x”为“sex”。不过，色情垃圾邮件发送者了解常见过滤器的局限性，并绕过它们。扫描图像很棘手。这就是为什么尽管内容过滤器经常存在缺陷，但学校别无选择，只能考虑它们。因为它们可能能够屏蔽以前未知的恶意网站。

Second method. The second method is based on lists of “good” and “bad” sites. A number of firms that do little but label websites send out regular updates of the “good” and “bad” lists to the subscribers, who may add their sites to the list.
  Search engines are a new area of concern, Google, by using the “cache” option on its  search result page, can allow its users to see websites without having actually to visit the sites. Google keeps copies of web pages on their site. Even after a website has been removed, Google may still be able to display its contents.
  Images are another area of concern. Google permits users to search for images without visiting the site from which the image resides. A student can enter the name of a famous person into a search engine’s image search engine and come up with a listing of nude and seminude images. One protective measure you can take with Google is to turn on its built-in filter called SafeSearch. This setting offers protection both against “adult” images and text.
  Few have the time to look for all the ways to evade the filters—but evidently students do. Which is why there is no effective substitute for simply watching the students. It’s not hard to spot the reaction when students stumble across pornography they should not have found. Hopefully, one can block that website in a short while. In addition, computer-based logging programs can be used to track student activity. If the students have found their way around the filter, the log files will indicate this. Throughout, the age of the student and concerns for privacy should be weighed against the student’s protection. For the protection required for a high school student differs than that for a third grader.  

关于使用过滤程序的争论在教育界引起了争议。支持过滤的倡导者认为，过滤器在阻止孩子进入不合适的网站方面做得很好。反对过滤的倡导者认为，过滤软件会阻止孩子进入包含合适信息但“不合适”词语的网站。过滤软件中使用的“道德指南针”也受到了质疑。人们认为，老师应该能够教孩子如何避免不合适的网站，而不必让孩子被过滤软件锁在网站之外。有效的组合是过滤系统、教育和警惕。虽然网络自由可能在中等教育中运作良好，但似乎将色情网站纳入小学教育存在太大风险。在这些网站上停留片刻就足以增加色情兴趣或开始对这种图像脱敏。因此，建议在小学阶段采用过滤系统、教学和警惕相结合的方法。教育工作者在场的存在不应该被低估。附近有老师在场，并且对学生在互联网上搜索的内容积极感兴趣，可以有效地阻止不合适的访问。将电脑放置在房间里，以便老师能够始终查看屏幕内容，也是一个很好的课堂威慑手段。

  Images, we noted above, are also a concern.  Student may enter the name of a famous person into a search engine’s image and retrieve questionable images. One protective measure you can use is to turn on SafeSearch a built-in filter that protects against both “adult” images and texts.
  Although it does not seem that one has the time to search for all the ways around the filters, students seem to find the ways. There is little option, then, but to simply watch the students and quickly block a questionable website. Also, you can also use computer-based log files to keep track of the activities of students. The age of the student and concerns for privacy should be weighed against the student’s right for privacy and protection-- the protection required for a high school student differs from that of a third grader.

PICS。正在处理这个问题的一个组织是互联网内容选择平台 (PICS)，该组织试图让父母控制孩子可以访问的材料类型。PICS 正在努力制定行业标准，用于允许根据互联网上所有网站和文档的内容对其适合儿童的程度进行评级。此外，该组织还将制定标准，使软件能够根据这些适合性评级来屏蔽网站。

   But not only schools and families! Businesses are also concerned with the type of Internet materials their workers assess over corporate networks. Retrieving and displaying sexual material can be interpreted as sexual harassment, and can lead to serious legal ramifications. In addition, most companies don’t want their workers accessing that material on company time. Some companies now lease the same software parents and schools are buying. Instead of installing the software on individual computers, however, the software is installed on a server, which checks all incoming Internet traffic to every computer in the company.

家长控制如何运作。（1）SurfWatch 软件会检查每个向 TCP/IP 堆栈传来的地址的 URL。它会搜索五种类型的 URL：http、nntp、ftp、gopher 和 IRC——这些 URL 最有可能包含令人反感的内容。它会将每个 URL 放入一个单独的“盒子”中。它允许其余传入的互联网数据通过。（2）SurfWatch 软件安装在父母想要监控的计算机上，以确保孩子无法访问互联网上的令人反感的内容。当孩子启动软件访问互联网时，SurfWatch 会根据使用的是 PC 还是 Macintosh，连接到 Winsock 或 MacTCP。一个 SurfWatch 软件模块位于 Winsock 或 MacTCP 的“前面”，监控到达 TCP/IP 堆栈的 TCP/IP 数据流。结论。尽管互联网上的儿童色情内容可能只占互联网内容的一小部分，但它对社会构成了巨大挑战。为了保护儿童免受儿童色情内容的侵害，使用过滤系统是阻止色情内容的有效方法。此外，主要服务器（如 AOL、Verizon 和 Time Warner）与父母、教育工作者和图书馆员之间的重要合作关系将进一步降低儿童色情内容的发生率。热线是接收公众投诉、为执法部门收集情报、从服务器中删除非法内容和提供安全教育的一种机制。简而言之，一项针对色情内容的有效合作关系正在形成。有关家长控制如何运作的摘要，请参见下面第 10 页的图示一和二。

  The oval-shaped Surf/Watch module looks for and screens http, nntp, ftp, gopher, IRC, which are most likely to contain objectionable material, from their respective boxes.
 SurfWatch checks thousands of sites and indexes those found to be objectionable. URLs in each of the boxes are checked against those from objectionable sites, blocking the site so that information can’t be viewed. 
 Not only images that offend but offensive words as well!  SurfWatch looking for objectionable words, pattern matching, alerts the child that the site has been blocked, preventing that information from being viewed. 
  In addition, SurfWatch employs a rating system, Platform for Internet Content Selection (PICS), to determine if objectionable material can be found among the documents. Objectionable material is blocked, preventing it from entering the TCP/IP stack. As above, the child is alerted that the site has been blocked.
  If the URL is not found objectionable, it is passed to the TCP/IP stack and then to the Internet software, where the child can view it and interact with it. SurfWatch does the checking instantaneously so there is no apparent delay in getting material from the Internet.
  Because of the furious growth of the Internet, new sites are created frequently. SurfWatch, to keep from being dated, automatically updates the data of sites every month, keeping the list of sites current.
  Businesses, to prevent workers from accessing objectionable sites over corporate networks, have the SurfWatch software installed on a site through which all Internet traffic must travel, filtering Internet traffic for the entire company.

参考文献 里布尔，迈克，& 贝利，杰拉德 (2007) 学校的数字公民。俄勒冈州尤金：ISTE

特里尔，塞恩·B. (2006) 资金有限的技术：教育工作者和其他专业人士的生存指南。纽约：教师学院出版社。

安全和负责任的互联网使用中心 http://csriu.org/about

教育工作者针对计算机犯罪和技术滥用的指南 www.uni.uiuc.edu/~dstone/educatorsguide.html

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首页-维基教科书，开放内容教科书的集合。

YouTube 访谈：卡桑德拉·迈达，高级技术培训师

以企业界为例，这位资深技术培训师表明，安全是其客户的主要关注点，但她能够通过提供一些具体细节并保持积极的态度来减轻他们的担忧。请记住，如果您试图向教师和家长推销您的系统——请保持积极的态度。不要列出所有可能出现的问题（这并不是说服人的有效方法），而要列出您计划采用的所有解决方案和安全措施。向这位企业培训师学习，在保持积极和自信的同时解决安全问题。

http://www.youtube.com/watch?v=IQpC53ByRc0

Kmr2136 (talk) 15:09, 10 March 2009 (UTC)

图表：家长控制如何运作（Gralla，2004，324）

选择题：1. 过滤系统的核心是：a. Gopher; b. ftp; c. SuperWatch; d. http。2. 最近同意禁止儿童色情的电缆公司：a. ESPN; b. Time Warner; c. Fox; ABC。3. 最有效地阻止儿童在互联网上观看色情内容的方法是：a. 有效的过滤系统; b. 立法行动; c. 自愿行动; d. 家长指导。4. 谷歌上允许儿童在互联网上观看色情内容的工具：a. 搜索; b. 雅虎; c. AltaVista; d. 缓存。

判断题：1. 由于有效的过滤系统，父母和教师在与儿童色情内容的斗争中无需保持警惕。T 或 F 2. 互联网用户可能会看到可疑网站，而无需访问该网站。T 或 F 3. 有效的过滤器被称为 SafeSearch。T 或 F 4. 对抗儿童色情内容最有效的工具是以下几种的组合：过滤系统；教育；警惕。T 或 F

选择题答案

1. 1- b (SurfWatch)
2. 2-b (Time Warner)
3. 3-a (过滤系统)
4. 4-c (缓存)

判断题答案

1. 1-F
2. 2-T
3. 3-T
4. 4-T