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计算机历史与发展英语作文英文回答：The History and Evolution of Computers.The history of computers dates back to the early days of human civilization. The first known computing devices were the abacus and the astrolabe, which were used by the ancient Greeks and Chinese for mathematical calculations and astronomy.In the 16th century, the invention of the mechanical calculator by Blaise Pascal marked a significant advancement in computing technology. This device could perform basic arithmetic operations, such as addition, subtraction, multiplication, and division.The 19th century saw the development of more advanced computing machines, such as the Analytical Engine by Charles Babbage. This machine was capable of performing awide range of mathematical operations and is considered to be the first mechanical computer.In the 20th century, the invention of the electronic computer revolutionized the field of computing. The first electronic computer, the ENIAC (Electronic Numerical Integrator and Computer), was developed by John Atanasoff and Clifford Berry at the University of Pennsylvania in 1943.The ENIAC was a massive machine that weighed over 30 tons and contained over 18,000 vacuum tubes. It was capable of performing complex calculations at a speed of 5,000 operations per second.The development of transistors in the late 1940s and early 1950s led to the creation of smaller and more powerful computers. The first transistorized computer, the TX-0, was developed by MIT in 1956.The 1960s and 1970s saw the development of integrated circuits (ICs), which allowed multiple transistors to bepacked onto a single silicon chip. This advancement led to the creation of even smaller and more powerful computers.The 1980s saw the release of the first personal computers (PCs), which brought computing power toindividual users for the first time. The IBM PC, releasedin 1981, was a particularly influential model that popularized the PC concept.The 1990s and early 2000s saw the development of the World Wide Web and the Internet, which connected computers around the world and revolutionized the way people communicated and accessed information.The 21st century has seen the rise of mobile computing, cloud computing, and artificial intelligence (AI). Mobile devices, such as smartphones and tablets, have become ubiquitous, providing users with access to computing power and connectivity on the go.Cloud computing allows users to access and store data and applications over the Internet, rather than on theirown devices. This provides greater flexibility and scalability.AI is a field of computer science that focuses on developing intelligent systems that can perform tasks typically requiring human intelligence, such as learning, problem-solving, and decision-making.The development of computers has had a profound impact on society. Computers have revolutionized the way we work, communicate, learn, and access information. They have also played a major role in scientific research, engineering, medicine, and many other fields.As computing technology continues to evolve, it is likely to have an even greater impact on our lives in the years to come.中文回答：计算机的历史与发展。
计算机英语作文Title: The Impact of Computers on Society。
In today's rapidly evolving world, computers play a pivotal role in shaping various aspects of society. From communication to education, from healthcare to entertainment, computers have revolutionized the way we live, work, and interact. In this essay, we will explore the profound impact of computers on society.First and foremost, computers have transformed the way we communicate. With the advent of the internet and social media platforms, people can connect with each other regardless of geographical boundaries. Email, instant messaging, and video calls have made communication more convenient and efficient than ever before. Additionally, social networking sites like Facebook, Twitter, and Instagram have redefined how we socialize and share information with others.Furthermore, computers have revolutionized the field of education. The availability of online courses and educational resources has made learning more accessible to people around the globe. Students can now access vast amounts of information with just a few clicks, allowing them to expand their knowledge and skills beyond the confines of traditional classrooms. Moreover, educational software and applications provide personalized learning experiences tailored to individual needs, enhancing the effectiveness of teaching and learning.In the realm of healthcare, computers have brought about significant advancements. Medical professionalsutilize computers for patient record management, diagnostic imaging, and treatment planning. Electronic health records (EHRs) streamline administrative tasks and improve the accuracy and efficiency of patient care. Additionally, medical researchers harness the power of computers for data analysis, drug discovery, and genetic research, leading to breakthroughs in disease prevention and treatment.Computers have also transformed the way we work and dobusiness. From small startups to multinational corporations, organizations rely on computers for various functions such as data analysis, project management, and customer relationship management. Cloud computing technology enables businesses to store and access data remotely, facilitating collaboration and increasing productivity. E-commerce platforms have revolutionized the retail industry, allowing consumers to shop online anytime, anywhere, and businessesto reach a global audience.Moreover, computers have had a profound impact on entertainment and media. Streaming services like Netflix, Hulu, and YouTube have changed the way we consume entertainment content, providing on-demand access to movies, TV shows, and videos. Video games, powered by sophisticated computer graphics and artificial intelligence, offer immersive experiences to players of all ages. Digital media platforms have also transformed the landscape of journalism and publishing, enabling anyone to create and share content with a global audience.However, along with the numerous benefits, computersalso pose certain challenges and concerns to society.Issues such as cybersecurity threats, data privacy breaches, and digital divide disparities need to be addressed to ensure the responsible and ethical use of technology. Furthermore, the increasing reliance on computers raises questions about job displacement due to automation and the potential societal implications of artificial intelligence.In conclusion, computers have undoubtedly reshaped society in profound ways, impacting how we communicate, learn, work, and entertain ourselves. While the benefits of computer technology are vast and undeniable, it isessential to address the challenges and ethical considerations that arise in its use. By harnessing the power of computers responsibly and ethically, we can leverage technology to create a more connected, informed, and prosperous society for generations to come.。
计算机类的英语作文模板Computer is a vital tool in today's society. It has revolutionized the way we live, work and communicate. As a result, the demand for computer professionals has increased significantly. In this essay, we will discuss the importance of computer education and the role it plays in shaping our future.Firstly, computer education is essential for students to succeed in the modern world. In today's society, computers are used in almost every aspect of life. From booking a flight to conducting research, computers have become an integral part of our lives. Therefore, it is crucial for students to have a basic understanding of computers and how they work. This will enable them to navigate the digital world with ease and confidence.Secondly, computer education plays a vital role in shaping our future. With the world becoming increasingly digital, computer skills are in high demand. By learningcomputer programming and coding, students can develop the skills needed to create innovative technologies that can change the world. For example, the development ofartificial intelligence and machine learning has transformed industries such as healthcare, finance, and transportation. Therefore, computer education is critical to the development of new technologies that can shape our future.Thirdly, computer education can provide students with a competitive edge in the job market. In today's competitive job market, having computer skills can make a significant difference. Many employers require basic computer skills, and some even require advanced skills such as programming and coding. Therefore, by learning computer skills, students can increase their chances of finding a job and advancing their careers.In conclusion, computer education is essential for students to succeed in the modern world. It plays a vital role in shaping our future and provides students with a competitive edge in the job market. Therefore, it iscrucial for schools to include computer education in their curriculum to prepare students for the digital world. With the right education, students can develop the skills needed to create innovative technologies that can change the world.。
计算机科技英语短文作文The Importance of Computer Science in Today's World。
In today's modern world, computer science plays a crucial role in almost every aspect of our lives. From the way we communicate and work to the way we access information and entertain ourselves, computer science has revolutionized the way we live. In this essay, we will explore the importance of computer science and its impact on our society.One of the most significant contributions of computer science is the way it has revolutionized communication. With the advent of the internet and social media, people can now connect with each other instantly, regardless of their location. This has not only made communication more convenient, but it has also opened up new opportunities for collaboration and networking. In addition, computer science has also made it possible for us to access and share information in ways that were unimaginable just a fewdecades ago.Another area where computer science has had a profound impact is in the field of education. With the rise ofonline learning platforms and educational software,students now have access to a wealth of resources that can help them learn and grow. This has not only made education more accessible, but it has also personalized the learning experience for many students. In addition, computer science has also made it possible for educators to track andanalyze student performance, allowing them to tailor their teaching methods to better meet the needs of their students.In the business world, computer science has also had a significant impact. From the way companies manage their operations to the way they reach and engage with customers, computer science has transformed the way business is done. With the rise of e-commerce and digital marketing, companies can now reach a global audience and conduct transactions with ease. In addition, computer science has also made it possible for businesses to streamline their operations and improve efficiency through the use ofautomation and data analysis.Furthermore, computer science has also had a profound impact on the field of healthcare. From the way medical records are stored and accessed to the way diagnoses are made and treatments are administered, computer science has revolutionized the way healthcare is delivered. With the rise of electronic medical records and telemedicine, patients now have access to better and more efficient care. In addition, computer science has also made it possible for researchers to analyze vast amounts of data and develop new treatments and therapies.In conclusion, computer science plays a crucial role in today's world, impacting almost every aspect of our lives. From the way we communicate and learn to the way we do business and receive healthcare, computer science has revolutionized the way we live. As technology continues to advance, the importance of computer science will only continue to grow, shaping the future of our society in profound ways.。
有关计算机的英语文章众所周知，计算机辅助教学在外语教学中起着越来越重要的作用。
随着学校的软硬件配备的不断完善，越来越多的外语教师开始从事计算机辅助教学的实践和研究。
下面是店铺带来的有关计算机的英语文章，欢迎阅读!有关计算机的英语文章篇一第三次计算机革命浪潮悄然来袭We have entered a new age of embedded, intuitive computing in which our homes, cars, stores, farms, and factories have the ability to think, sense, understand, and respond to our needs. It's not science fiction, but the dawn of a new era.我们正在迈入可穿戴、直觉式计算的新时代。
房屋、汽车、商店、农场、工厂，这些东西都将具备思考、感知和行动的能力。
这不是科幻小说中的场景，而是我们即将进入的新时代。
Most people might not realize it yet, but we are already feeling the impact of what's known as the third wave of computing. In small but significant ways it is helping us live safer, healthier, and more secure lives. If you drive a 2014 Mercedes Benz, for example, an "intelligent" system endeavors to keep you from hitting a pedestrian. A farmer in Nigeria relies on weather sensors that communicate with his mobile device. Forgot your medication? A new pill bottle from AdhereTech reminds you via text or automated phone messages that it's time to take a pill.大多数人可能还没有意识到，我们已经感受到第三次计算机革命的影响。
关于计算机的英语文章随着现代信息技术的迅猛发展，计算机已经广泛地应用到社会的各行各业，人们渴望学习这种“人类通用智力工具”。
下面是店铺带来的关于计算机的英语文章，欢迎大家阅读!关于计算机的英语文章篇一系统软件Software refers to computer programs. Programs are the instructions that tell the computer how to process data into the form you want. There are two kinds of software: system software and application software.软件指的是计算机程序。
程序是告诉计算机如何将数据处理成你想要的形式的指令。
有两种软件：系统软件和应用软件。
System software is a collection of programs that enables application software to run on a computer system's hardware devices, it is background software and includes programs that help the computer manage its own internal resources.系统软件是指能让应用软件在计算机系统硬件设备上运行的程序的集合，它是后台软件并且包括帮助计算机管理自己内部资源的程序。
Application software is a specialized programs that enables the user toaccomplish specific tasks.应用软件是让用户能够完成特定任务的专门程序。
In this text, we mainly discuss system software.System software consists of four kinds of programs: bootstrap loader, diagnostic routines, basic input-output system, and operating system. Among these four parts, the operating system is we most concerned with, whith helps manage computer resources. Most important operating systems are: Windows, Windows NT, OS/2, Macintosh, and Unix.在这一节中，我们主要讨论系统软件。
计算机英语毕业论文计算机英语用语增进了用户亲切感的原因之一是隐喻的使用。
把新技术比喻成人人熟知的旧东西对承受计算机压力(technostress)的人有很大帮助。
下面是店铺给大家推荐的计算机英语毕业论文，希望大家喜欢!计算机英语毕业论文篇一《计算机英语新用语》摘要：随着计算机科学技术的发明和普及，出现了大量的新英语词汇，还使许多原有的英语词被赋予新意。
计算机英语新词汇有其特点、结构和变化，也有一些认识、学习和运用的规律。
本文就计算机英语新用语进行了阐述。
关键词：计算机英语新词汇隐喻结构变化计算机的发展日新月异，人们不可避免地要与计算机打交道。
现在如果你想真正地掌握英语这门语言，就必须熟悉那些随处可见的新计算机英语词汇。
例如，你若是天天坐在电脑桌前，在英语中被称为mouse potato;或者你对计算机新技术感到紧张不安则被称为technophobe。
值得庆幸的是，大多数计算机英语用语并不难学，一方面是因为其中的许多词已经出现在人们的语言中了，像汉语中mouse译为鼠标;德语与computer相对应的词是Computer;西班牙语则是computador。
另一方面，计算机英语新词汇的丰富多彩也是人们容易学习的原因。
比如一些词语snail mail(传统书信而不是电子邮件)，或wysiwyg(what-you-see-is-what-you-get你看到的就是你得到的)，会让第一次听说的人发笑。
计算机英语用语增进了用户亲切感的原因之一是隐喻的使用。
把新技术比喻成人人熟知的旧东西对承受计算机压力(technostress)的人有很大帮助。
因为许多人害怕使用电脑，隐喻对帮助用户适应计算机技术起着重要作用，例如，cut和paste(剪贴)计算机数据时，人们会想到纸张的使用;看到desktop，file，folder，recycle bin，wallpaper等词时，人们会想到自己熟悉的办公室。
计算机隐喻很有趣，因为许多与主题相关，像办公室主题。
描述计算机专业的作文英语Computer Science Major。
As technology continues to advance at a rapid pace, the field of computer science has become increasingly important. Computer science is the study of computers andcomputational systems, including their design, development, and use. It is a highly interdisciplinary field that combines aspects of mathematics, engineering, and science.As a computer science major, students will learn about the fundamentals of computing, including programming languages, algorithms, data structures, and computer architecture. They will also study software engineering, database systems, operating systems, and computer networks. In addition, students will develop problem-solving skills and learn to think critically about complex systems.One of the most important skills that computer science majors will learn is programming. Programming is theprocess of creating software and applications using various programming languages such as Java, Python, and C++. Students will learn how to write code, debug programs, and develop software applications. They will also learn about software development methodologies such as agile and waterfall.Another important aspect of computer science is data analysis. With the vast amount of data available today, it is essential for computer scientists to be able to analyze and interpret data. Students will learn about data mining, machine learning, and artificial intelligence. They will also learn how to use statistical tools and techniques to analyze data.As computer science is a rapidly evolving field, students will need to keep up to date with the latest developments and trends. This requires a strong commitment to lifelong learning and professional development. Students will need to be proactive in seeking out new opportunities for learning and networking with other professionals in the field.In conclusion, a computer science major is an excellent choice for students who are interested in technology and want to make a difference in the world. With a solid foundation in programming, data analysis, and problem-solving, computer science majors are well-equipped to tackle the complex challenges of the modern world.。
关于计算机英语作文Title: The Evolution of Computers: From Abacus to Quantum Computing。
Computers have revolutionized every aspect of human life, from communication to transportation, healthcare to entertainment. This essay explores the evolution of computers, tracing their journey from simple calculating devices to the potential of quantum computing.The earliest known computing device is the abacus, invented over 5,000 years ago. It allowed for basic arithmetic calculations through the manipulation of beads on rods. Fast forward to the 19th century, and we encounter mechanical calculators like Charles Babbage's Analytical Engine, which laid the groundwork for modern computers with its ability to perform various mathematical operations.The true dawn of modern computing arrived in the 20th century with the advent of electronic computers. The firstprogrammable electronic computer, the ENIAC (Electronic Numerical Integrator and Computer), was developed during World War II to calculate artillery firing tables. Its creation marked a paradigm shift, introducing electronic components and binary code to perform complex calculations at unprecedented speeds.Following the ENIAC, the development of transistors in the late 1940s paved the way for smaller, faster, and more reliable computers. This led to the birth of the first commercially successful computer, the UNIVAC (Universal Automatic Computer), which further propelled the digital revolution.The 1970s witnessed the emergence of personal computers (PCs), thanks to pioneers like Apple and IBM. These machines brought computing power to individuals and small businesses, transforming the way people work and interact. The graphical user interface (GUI) introduced by Apple's Macintosh in 1984 made computers more accessible to the general public, significantly impacting user experience.The 1990s saw the rise of the internet, connecting computers worldwide and giving birth to the digital age. This period also witnessed advancements in microprocessor technology, leading to faster and more efficient computers. The integration of multimedia capabilities further expanded the range of applications, from gaming to multimedia content creation.As we entered the 21st century, computing entered the era of mobility with the proliferation of smartphones and tablets. These devices combined computing power with portability, enabling users to access information and perform tasks on the go. Cloud computing emerged as a dominant trend, offering scalable and cost-effective solutions for storage and computation.Looking ahead, one of the most exciting frontiers in computing is quantum computing. Unlike classical computers that use bits to represent data as either 0 or 1, quantum computers leverage quantum bits or qubits, which can exist in multiple states simultaneously due to the principles of quantum mechanics. This enables quantum computers toperform certain calculations exponentially faster than classical computers.Quantum computing holds the promise of revolutionizing fields such as cryptography, drug discovery, and optimization. Researchers and tech giants are racing to develop practical quantum computers capable of solvingreal-world problems. While significant challenges remain, such as qubit stability and error correction, the potential impact of quantum computing on society cannot be overstated.In conclusion, the evolution of computers has been marked by continuous innovation and technological breakthroughs. From the humble abacus to the potential of quantum computing, computers have transformed the way we live, work, and communicate. As we stand on the brink of a new computing era, it is fascinating to imagine the possibilities that lie ahead.。
计算机英语四级作文Computers and Our Life。
With the development of technology, computers have become an indispensable part of our life. They have brought us countless benefits and greatly improved our efficiency and productivity. However, they also have some negative effects on our life.On the one hand, computers have made our life more convenient and efficient. They can help us with a variety of tasks, such as sending emails, browsing the internet, and creating documents. They have also made communication easier and faster, allowing us to connect with people all over the world in real time. In addition, computers have revolutionized the way we work, making it possible to work from home or on the go, and saving us time and money.On the other hand, computers have also had some negative effects on our life. One of the biggest problemsis that they can be addictive. Many people spend hours each day on their computers, neglecting their work, family, and friends. This can lead to social isolation and other health problems, such as eye strain and back pain. In addition, computers can also be a source of distraction, making it difficult to focus on important tasks and causing us to waste time on unimportant things.Despite these negative effects, computers have become an essential part of our life, and we cannot imagine living without them. As such, it is important that we learn to use them responsibly, and find a balance between their benefits and drawbacks. We should also be aware of the potential risks and take steps to protect ourselves, such as using anti-virus software and avoiding suspicious websites.In conclusion, computers have had a profound impact on our life, both positive and negative. While they have brought us many benefits, they also have some drawbacksthat we need to be aware of. By using them responsibly and finding a balance between their benefits and drawbacks, wecan continue to enjoy the many benefits that computers have to offer.。
电子计算机英语论文Security of Computer Network System---------------------------------------------------------------------------------------计算机网络安全浅析摘要：针对计算机网络系统存在的安全性和可靠性问题，本文从网络安全的重要性、理论基础、具备功能以及解决措施等方面提出一些见解，并且进行了详细阐述，以使广大用户在计算机网络方面增强安全防范意识。
关键词：计算机网络虚拟专用网技术加密技术防火墙引言：随着计算机网络技术的发展，网络的安全性和可靠性已成为不同使用层次的用户共同关心的问题。
人们都希望自己的网络系统能够更加可靠地运行，不受外来入侵者干扰和破坏。
所以解决好网络的安全性和可靠性问题，是保证网络正常运行的前提和保障。
一、网络安全的重要性。
在信息化飞速发展的今天，计算机网络得到了广泛应用，但随着网络之间的信息传输量的急剧增长，一些机构和部门在得益于网络加快业务运作的同时，其上网的数据也遭到了不同程度的攻击和破坏。
攻击者可以窃听网络上的信息，窃取用户的口令、数据库的信息；还可以篡改数据库内容，伪造用户身份，否认自己的签名。
更有甚者，攻击者可以删除数据库内容，摧毁网络节点，释放计算机病毒等等。
这致使数据的安全性和自身的利益受到了严重的威胁。
根据美国FBI（美国联邦调查局）的调查，美国每年因为网络安全造成的经济损失超过170亿美元。
75%的公司报告财政损失是由于计算机系统的安全问题造成的。
超过50%的安全威胁来自内部。
而仅有59%的损失可以定量估算。
在中国，针对银行、证券等金融领域的计算机系统的安全问题所造成的经济损失金额已高达数亿元，针对其他行业的网络安全威胁也时有发生。
由此可见，无论是有意的攻击，还是无意的误操作，都将会给系统带来不可估量的损失。
所以，计算机网络必须有足够强的安全措施。
无论是在局域网还是在广域网中，网络的安全措施应是能全方位地针对各种不同的威胁和脆弱性，这样才能确保网络信息的保密性、完整性和可用性。
二、网络安全的理论基础。
国际标准化组织（ISO）曾建议计算机安全的定义为：“计算机系统要保护其硬件、数据不被偶然或故意地泄露、更改和破坏。
”为了帮助计算机用户区分和解决计算机网络安全问题，美国国防部公布了“桔皮书”（orange book，正式名称为“可信计算机系统标准评估准则”），对多用户计算机系统安全级别的划分进行了规定。
桔皮书将计算机安全由低到高分为四类七级：D1、C1、C2、B1、B2、B3、A1。
其中D1级是不具备最低安全限度的等级，C1和C2级是具备最低安全限度的等级，B1和B2级是具有中等安全保护能力的等级，B3和A1属于最高安全等级。
在网络的具体设计过程中，应根据网络总体规划中提出的各项技术规范、设备类型、性能要求以及经费等，综合考虑来确定一个比较合理、性能较高的网络安全级别，从而实现网络的安全性和可靠性。
三、网络安全应具备的功能。
为了能更好地适应信息技术的发展，计算机网络应用系统必须具备以下功能：（1）访问控制：通过对特定网段、服务建立的访问控制体系，将绝大多数攻击阻止在到达攻击目标之前。
（2）检查安全漏洞：通过对安全漏洞的周期检查，即使攻击可到达攻击目标，也可使绝大多数攻击无效。
（3）攻击监控：通过对特定网段、服务建立的攻击监控体系，可实时检测出绝大多数攻击，并采取响应的行动（如断开网络连接、记录攻击过程、跟踪攻击源等）。
（4）加密通讯：主动地加密通讯，可使攻击者不能了解、修改敏感信息。
（5）认证：良好的认证体系可防止攻击者假冒合法用户。
（6）备份和恢复：良好的备份和恢复机制，可在攻击造成损失时，尽快地恢复数据和系统服务。
（7）多层防御：攻击者在突破第一道防线后，延缓或阻断其到达攻击目标。
（8）设立安全监控中心：为信息系统提供安全体系管理、监控、保护及紧急情况服务。
四、网络系统安全综合解决措施。
要想实现网络安全功能，应对网络系统进行全方位防范，从而制定出比较合理的网络安全体系结构。
下面就网络系统的安全问题，提出一些防范措施。
物理安全可以分为两个方面：一是人为对网络的损害；二是网络对使用者的危害。
最常见的是施工人员由于对地下电缆不了解，从而造成电缆的破坏，这种情况可通过立标志牌加以防范；未采用结构化布线的网络经常会出现使用者对电缆的损坏，这就需要尽量采用结构化布线来安装网络；人为或自然灾害的影响，需在规划设计时加以考虑。
访问控制安全，访问控制识别并验证用户，将用户限制在已授权的活动和资源范围之内。
网络的访问控制安全可以从以下几个方面考虑。
（1）口令：网络安全系统的最外层防线就是网络用户的登录，在注册过程中，系统会检查用户的登录名和口令的合法性，只有合法的用户才可以进入系统。
（2）网络资源属主、属性和访问权限：网络资源主要包括共享文件、共享打印机、网络通信设备等网络用户都有可以使用的资源。
资源属主体现了不同用户对资源的从属关系，如建立者、修改者和同组成员等。
资源属性表示了资源本身的存取特性，如可被谁读、写或执行等。
访问权限主要体现在用户对网络资源的可用程度上。
利用指定网络资源的属主、属性和访问权限可以有效地在应用级控制网络系统的安全性。
（3）网络安全监视：网络监视通称为“网管”，它的作用主要是对整个网络的运行进行动态地监视并及时处理各种事件。
通过网络监视可以简单明了地找出并解决网络上的安全问题，如定位网络故障点、捉住IP盗用者、控制网络访问范围等。
（4）审计和跟踪：网络的审计和跟踪包括对网络资源的使用、网络故障、系统记帐等方面的记录和分析。
一般由两部分组成：一是记录事件，即将各类事件统统记录到文件中；二是对记录进行分析和统计，从而找出问题所在。
数据传输安全，传输安全要求保护网络上被传输的信息，以防止被动地和主动地侵犯。
对数据传输安全可以采取如下措施：（1）加密与数字签名：数字签名是数据的接收者用来证实数据的发送者确实无误的一种方法，它主要通过加密算法和证实协议而实现。
（2）防火墙：防火墙（Firewall）是Internet上广泛应用的一种安全措施，它可以设置在不同网络或网络安全域之间的一系列部件的组合。
它能通过监测、限制、更改跨越防火墙的数据流，尽可能地检测网络内外信息、结构和运行状况，以此来实现网络的安全保护。
（3）User Name/Password认证：该种认证方式是最常用的一种认证方式，用于操作系统登录、telnet（远程登录）、rlogin（远程登录）等，但此种认证方式过程不加密，即password 容易被监听和解密。
（4）使用摘要算法的认证：Radius（远程拨号认证协议）、OSPF（开放路由协议）、SNMP Security Protocol等均使用共享的Security Key（密钥），加上摘要算法（MD5）进行认证，但摘要算法是一个不可逆的过程，因此，在认证过程中，由摘要信息不能计算出共享的security key，所以敏感信息不能在网络上传输。
市场上主要采用的摘要算法主要有MD5和SHA-1。
（5）基于PKI的认证：使用PKI（公开密钥体系）进行认证和加密。
该种方法安全程度较高，综合采用了摘要算法、不对称加密、对称加密、数字签名等技术，很好地将安全性和高效性结合起来。
这种认证方法目前应用在电子邮件、应用服务器访问、客户认证、防火墙认证等领域。
该种认证方法安全程度很高，但是涉及到比较繁重的证书管理任务。
（6）虚拟专用网络（VPN）技术：VPN技术主要提供在公网上的安全的双向通讯，采用透明的加密方案以保证数据的完整性和保密性。
总结：综上所述，对于计算机网络传输的安全问题，我们必须要做到以下几点。
第一，应严格限制上网用户所访问的系统信息和资源，这一功能可通过在访问服务器上设置NetScreen 防火墙来实现。
第二，应加强对上网用户的身份认证，使用RADIUS等专用身份验证服务器。
一方面，可以实现对上网用户帐号的统一管理；另一方面，在身份验证过程中采用加密的手段，避免用户口令泄露的可能性。
第三，在数据传输过程中采用加密技术，防止数据被非法窃取。
一种方法是使用PGP for Business Security对数据加密。
另一种方法是采用NetScreen 防火墙所提供的VPN技术。
VPN在提供网间数据加密的同时，也提供了针对单机用户的加密客户端软件，即采用软件加密的技术来保证数据传输的安全性。
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[2] 杜飞龙，Internet原理与应用，人民邮电出版社，1997。
[3] 胡道元，信息网络系统集成技术，清华大学出版社，1995。
[4] 杨明福，计算机网络，电子工业出版社，1998.5。
[5] 袁保宗，因特网及其应用，吉林大学出版社，2000。
[6] 隋红建等，计算机网络与通信，北京大学出版社,，1996。
[7] 周明天等，TCP/IP网络原理与应用，清华大学出版社，1993。
[8] 计算机学报，1998-2001。
[9] 网络报，1997-2001。
Security of Computer Network SystemAbstract: This paper discussed the secure and dependable problem about the computer network system. On some aspects: the importance of network security, basic theory, function, and the method of solving a problem, etc. Good views for solving the problem are put forward. It strengthens people’s consciousness on network security.Key words: Computer network Virtual private network Encryption techniques Firewall Introduction:Along with the computer network technology development, the network security and the reliability have become the question of common interest by all users. The people all hoped their own network system can move reliably, not external intruder disturbance and destruction. Therefore solves the network security and the reliable problem carefully, is a guarantee the network normal operation’s premise and safeguard.First, the importance of the network security. With the informationization developing fast today, the computer network obtained the widespread application, but along with the network information transmission capacity growing faster, some organizations and departments benefit the speedup with the service operation in the network, while, the data has also suffered to extent attack and destruction. The aggressor may intercept the information in the network, steals the user’s password, the database information; also may tamper with the database content, the forge user’s status, denies own signature. And what is more, the aggressor may delete t he database content, the destroy node, releases computer virus and so on. This cause data security and own benefit have received the serious threat.According to American FBI (US Federal Bureau of Investigation) investigation, the network security creates the economic loss surpasses 17,000,000,000 dollars every year.75% corporation report finance loss is because the computer system security problem creates. More than 50% safe threat come from inside. But only 59% loss could be possible estimate. In China, the economic loss amount in view of financial domain and the bank, negotiable securities computer system security problems creates has reached as high as several hundred million Yuan, also sometimes occurs in view of other profession network security threat.Thus it can be seen, regardless of is the mean attack, or unconscious disoperation, will all be able to bring the inestimable loss to the system. Therefore, the computer network must have the enough strong security measure. Regardless of is in the local area network or in WAN, the network security measure should be Omni-directional in view of each kind of different threat and the vulnerability, so that it can guarantee the network information’s secrecy, the integrity and the usability.Second, network security rationale. International Standardization Organization (ISO) once suggested the computer security the definition was: “The computer system must protect its hardware, the data not accidentally or reveals intentionally, the change and the destruction.” In order to help the computer user discrimination and the solution computer network security problem, the American Department of Defense announced “the orange peel book” (orange book, official name is “credible computer system standard appraisal criterion”), has carried on the stipulation to the multiuser computer system security rank division.The orange peel book from low to high divides into the computer security four kinds of seven levels: D1, C1, C2, B1, B2, B3, A1.Above all,D1 level does not have the lowest safety marginrank, C1 and the C2 level has the lowest safety margin rank, B1 and the B2 level has the medium safekeeping of security ability rank, B3 and A1 belongs to the highest security rating.In the network concrete design process, it should act according to each technology standard, the equipment type, the performance requirement as well as the funds which in the network overall plan proposed and so on, the overall evaluation determines one quite reasonably, the performance high network security rank, thus realization network security and reliability.Third, the network security should have function. In order to adapt the information technology development well, the computer network application system must have following function:(1)Access control: Through to the specific webpage, the service establishment accesscontrol system, in arrives the overwhelming majority attack impediment in front ofthe attack goal.(2)Inspects the security loophole: Through to security loophole cyclical inspection, even ifattacks may get the attack goal, also may cause the overwhelming majority attack tobe invalid.(3)Attack monitoring: Through to specific webpage, service establishment attackmonitoring system, but real-time examines the overwhelming majority attack, andadopts the response the motion (for example separation network connection,recording attack process, pursuit attack source and so on).(4)Encryption communication: Encrypts on own initiative the communication, may enablethe aggressor to understand, the revision sensitive information.(5)Authentication: The good authentication system may prevent the aggressor pretends thevalidated user.(6)Backup and restoration: The good backup and restores the mechanism, may causes thelosses when the attack, as soon as possible restores the data and the system service.(7)Multi-layered defense: The aggressor after breaks through the first defense line delays orblocks it to reach the attack goal.(8)Sets up the safe monitoring center: Provides the security system management, themonitoring, the protection and the emergency case service for the informationsystem.Fourth, the network system safety comprehensive solution measures. If want to realize the network security function, we should carry on the Omni-directional guarding to the network system, and thus formulate the quite reasonable network security architecture. Below on the network system security problem, proposes some guard measure.Physics safe may divide into two aspects: One is the artificial harm to the network; the other is the network to the users. Most common thing is the constructor who did not understand to the buried cable clearly, thus lead to the destruction of electric cable, this kind of situation may through standing symbolized the sign guards against; Has not used the structurized wiring the network to be able to appear the user frequently to the electric cable damage, this needs to use the structurized wiring to install the network as far as possible; Artificial or natural disaster influence, when to consider the plan.The access control security, the access control distinguishes and confirms the user, limits the user in the already activity and the resources scope which is authorized. The network access control safe may consider from following several aspects.(1)password: The network security system most outer layer defense line is network user'sregistering, in the registration process, the system would inspect the user to registerthe name and the password validity, only then the legitimate user can enter the system.(2)The network resources’ host, the attribute and the visit jurisdiction: The networkresources mainly include the resources which shared files, the shared printer, networkusers and so on, that all the network users can use. The resources were the host tomanifest the different user to the resources subordinate relations, such as builder,modifier and group member and so on. The resources attribute expressed itself depositand withdrawal characteristics, as can read by who, write or the execution and so on.The visit jurisdiction mainly manifests in the user to the network resources availabledegree in using assigns the network resources to be the host, the attribute and thevisit jurisdiction may effectively in the application cascade control network systemsecurity.(3)Network security surveillance: The network surveillance is generally called for “thenetwork management”, its function mainly is carries on the dynamic surveillance tothe entire network movement and handles each kind of event promptly. Mayunderstand simply through the network surveillance discovers and solves in thenetwork security problem, such as the localization network fault point, seizes the IPembezzler, the control network visit scope and so on.(4)Audit and track: Network audit and track which is including the network aspect,resources use, network breakdown and system keeping. It composed generally by twoparts: One, the recording event, soon each kind of event entirely records in thedocument; Two, carries on the analysis and the statistics to the recording, thusdiscovers the question to be at.The data transmission security, the transmission safety requirements protect the information which is transmitting, prevented passively and encroaches on own initiative. We may take the following measure to the data transmission:(1)Encryption and digital signature: The digital signature which is the data receiverconfirms the data transmission truly and unmistakable, it mainly realizes through theencryption algorithm and the confirmation agreement.(2)Firewall: Firewall is a security measure which is widespread use on the Internet, it mayestablish in different network or between a series of part combination. It can throughthe monitor, the limit, the change surmounts the firewall’s data stream, it examinesthe information inside and outside as far as possible, so that realizes the networksafekeeping of security.(3)User Name/Password Authentication: This authentication is the most commonly used, ituses in the operating system registering, telnet (long-distance registers) rlogin(long-distance registers) and so on, but this kind of authentication way process doesnot encrypt, namely password is monitored easily and deciphered.(4)Use abstract algorithm authentication: Radius (long-distance digit dialing authenticationagreement), OSPF (opening route agreement), SNMP Security Protocol and so on,these all use sharing Security Key (key), in addition the abstract algorithm (MD5)carries on the authentication, but the abstract algorithm is an irreversible process,therefore, in the authentication process, cannot calculate sharing by the abstractinformation security key, therefore the sensitive information cannot transmit in thenetwork. In the market mainly uses the abstract algorithm mainly has MD5 andSHA-1.(5)Based on PKI authentication: Uses PKI (public key system) to carry on theauthentication and the encryption. This method safety rate is high, the synthesis usedthe abstract algorithm, has encrypted asymmetrically, symmetrical technologies andso on encryption, digital signature, well security and highly effective union. Thisauthentication method applies at present in the email, the application server visit, thecustomer authentication, the firewall Domains and so on authentication. This kind ofauthentication method safety rate is very high, but involves to the quite arduouscertificate management duty.(6)Hypothesized private network (VPN) technology: The VPN technology mainly provideson the public network the security bidirectional communication uses the transparentdecipherment scheme to guarantee the data the integrity and the secrecy. Summary:Generally speaking, the security problem which transmits regarding the computer network, we must have to achieve following points. First, we should strictly limit the system information and the resources which the surfer user visits; this function may through the visit on the server to establish the Net Screen firewall to realize. Second, we should strengthen to the user's status authentication, and we can use RADIUS which is the special-purpose identification authentication server. At the same time, it may realize to manage the user’s account; On the other hand, uses the encryption in the identification authentication process the method, avoids the user password revelation the possibility. Third, uses the encryption technology in the data transmission process, prevented the data illegal is stolen. One method is uses PGP for Business Security to encrypt to the data. Another method uses the VPN technology which the Net Screen firewall provides.VPN while provides between the net data encryption, also has provided in view of the single plane user's encryption client side software, and namely uses the software encryption the technology to guarantee the data transmission the security.Reference:[1] Cai Wandong, Computer network technology. Xian University press, 1988.[2] Du Feilong, Internet principle and application, people's posts and telecommunications press, 1997.[3] Hu Daoyuan, Information network system integration technology, the Qinghua University press, 1995.[4] Yang mingfu, Computer network, electronics industry press, 1998.5.[5] Yuan Baozong, Internet and application, Jilin University press, 2000.[6] Sui Hongjian and so on, Computer network and correspondence, Beijing University press, 1996.[7] Zhou tianming and so on, TCP/IP network theorem and application, Qinghua University press, 1993.[8] Chinese Journal of Computers, 1998-2001.[9] Network newspaper, 1997-2001.。
