局域网毕业论文文献翻译中英文对照.doc

外文资料及中文译文院系名称 信息科学与技术学院 学生姓名 学生学号 _ 200503013098 专业班级 _ 计科03- 7 指导教师 外文资料出处：计算机世界报 第03期 C20A LAN may be created based on a peering or a client-server. Small LANs are of ten created based on a simple peering relationship. Users may share resources and communicate with one another on a peer network, but no single computer controls a peer network, and peer network users do not typically centralize files on one machine. As a rule, peer networks tend to lack organization and adequate security controls.The client-server architecture is usually used for sever controls network access and network resources. Clients request resources from the server, and the server provides resources to clients. Servers may range in complexity from mainframes to PCs. Clients may range in complexity from PCs to display to terminals (DTS). Client-Server networks provide strong central security, centralized file organization and storage, and centralized data preservation. Compared to a peer network, a client-server network requires more centralized and specialized administration.Along with the rapid scientific and technological development, computer use in production as a proportion growing, increasingly play a decisive role in the ministry, the office has computers, greatly facilitate the department's work, another demand gradually reveal themselves. That is the single transmission of information between. Computer networks should be established as soon as possible on the agenda. Establish computer networks main purpose is to realize a "resource sharing" that all network users can enjoy the computer systems of all or part of the resources.LAN are currently used to broadcast the technical basis for Ethernet, any two nodes of communication between the data packet is not only these two nodes by the card receipt, were also at the same Ethernet to the nodes of a network card by the interception, As long as hackers access to the Ethernet nodes for an interception, can capture the Ethernet in the data packet and all its packet analysis solution, thereby stealing critical information, This is the Ethernet inherent security risks. In fact, many on the Internet free of the hacking tools are put Ethernet interception as the most fundamental means. A firewall is a network device that enforces security policy for network traffic. The term originates from firewall, a fireproof wall used as a barrier to prevent the spread of fire. An Internet firewall creates a barrier between separate networks by imposing a point of control that traffic needs to pass before it can reach a different network. A firewall may limit the exposure of hosts to malicious network traffic, e.g., remote adversaries attempting to exploit security holes in vulnerable applications, by preventing certain packets from entering networks protected by the firewall.When inspecting a network packet, a firewall decides if it should drop or forward the packet. The decision is based on a firewall's security policy and its internal state. Before forwarding a packet, a firewall may modify the packet's content. Packet inspection may occur at several different layers: (1)The link layer provides physical addressing of devices on the same network. Firewalls operating on the link layer usually drop packets based on the media access control (MAC) addresses of communicating hosts. (2)The network layer contains the Internet protocol (IP) headers that support addressing across networks so that hosts not on the same physical network can communicate with each other. (3)The transport layer provides data flows between hosts. On the Internet, the transmission control protocol (TCP) and the user datagram protocol (UDP) are used for this purpose. Most firewalls operate at the network and transport layer. TCP provides reliable data flow between hosts. UDP is a much simpler but unreliable transport protocol. (4)The application layer contains application specific protocols like the hypertext transfer protocol (HTTP). Inspection of application specific protocols can be computationally expensive because more data needs to be inspected and more states are required. A firewall is a piece of software or hardware that helps screen out hackers, viruses, and worms that try to reach your computer over the Internet. If you are a home user or small-business user, using a firewall is the most effective and important first step you can take to help protect your computer. It is important to have a firewall and antivirus software turned on before you connect to the Internet. If your computer is not protected when you connect to the Internet, hackers can gain access to personal information on your computer. They can install code on your computer that destroys files or causes malfunctions. They can also use your computer to cause problems on other home and business computers connected to the Internet. A firewall helps to screen out many kinds of malicious Internet traffic before it reaches your system. Some firewalls can also help to prevent other people from using your computer to attack other computers without your knowledge. Using a firewall is important no matter how you connect to the Internet dial-up modem, cable modem, or digital subscriber line (DSL or ADSL). The firewall product main bastion of the mainframe, packet-filtering router, Application Layer Gateway (Proxy), and Circuit Gateway, shielding mainframe firewalls, and other mainframe-type places. Although the firewall is to protect the network from hacker attacks effective means, but there are clearly inadequate: unable to prevent outside the firewall through other means of attack, not prevent defection from within and not attentive to the customers who brought the threat, able to completely prevent transmission of the virus has infected software or documents, and can not prevent data-driven attacks. Since 1986 digital companies in the United States to install the Internet world, a commercial fire Wall system, the concept of a firewall after firewall technology has made rapid development. Dozens of domestic and foreign companies launched the function of the firewall is not the same product range. 5 firewall at the network layer security system at the bottom of belonging to the network layer security technology areas. In this layer, the business-to-security system raised of the question: whether all the IP can visit to the enterprise's internal network? If the answer is "yes", is illustrated in internal network has no network layer take preventive measures. As the internal network and external public network between the first barrier Firewall is the first by the people's attention to the network security products in one. Although theoretically, firewall network security at the bottom, the network responsible for the security authentication and transmission, But with network security technology development and application of the network changes, Modern technology has gradually firewall to the network layer other than the safety level, not only to complete the traditional firewall filtering tasks, but also for the various networks to provide the corresponding security services. In addition there is many other firewall products are moving towards data security and user authentication, anti-virus and hacker intrusion direction. SMEs in the specific network environment, in addition to HIV and the birthright of transmissibility, enforceability, and conventional destructive virus in common, but also have some other features: 1. Faster rate of infection The spread of the virus must be some means for the complete closure of the single case; the virus is not from one computer to another computer transmission of. But the simple enterprise network environment, the spread of the virus can fully use the media, simple and rapid adoption of the internal network, the virus can spread rapidly, for example: Common in the 100 M office network, as long as one is exposed workstations, can be in the tens of seconds to the same network of several hundred computers infected all. 2. Wide spread Infection of a particular LAN client Taiwan, and the client can also further infection of other network client (including servers) infected with the virus and the client can further infection more client (including a computer outside the LAN) so many cross-infection, the virus spread in the network, in addition to speed, its spread is quite amazing. 3. Dissemination in the form of complex and diverse Network forms of transmission of the virus before we have already done a presentation here would not elaborate on the But with computer viruses innovation, I believe there will be even more we can not predict the form of dissemination. 4. Difficult to eradicate Single of computer viruses can sometimes through anti-virus and virus deleted documents to resolve. If that does not work, such as low-level disk formatting can measure the complete removal of the virus. Network, as long as they have a workstation could not cleanse, the whole network can be re-infected with the virus, have just completed a work of the anti-virus workstations, it may be another virus Internet workstations are infected. Therefore, to deal with the single form of anti-virus, the LAN will be more pronounced, felt helpless. 5. Devastating SMEs office network is mainly for enterprise services. Virus attacks, the network will not only affect their normal work, and even more frightening is that it would collapse the network, damage to the computer network, so that work was ruined. 6. Sexual sparks It can be described as the hidden nature of the virus on the network extension, the network conditions for the virus to stimulate the diversification, it is the internal clock, the date and user name, it can also be a network of communication and so on. An HIV virus in accordance with the procedures designers, at the request of a workstation outbreak and spread to the entire network. 7. Potential In the network, once infected with the virus, even if the virus has been eliminated, the potential danger is enormous. According to the company's network statistics, the virus has been removed, 85% of the 30 days will be re-infection. Enterprises still using single version of anti-virus software virus defense at the same time, virus has in various forms through the LAN to spread quickly, and they attacked the client, server, and gateway, almost all pervasive. it is not exaggerating to say, we can easily make the entire LAN gridlock, should we really have to sit until death?Although the prospect of using virus technology to simplify the task of delivering patches and software updates is tempting, the dangers can outweigh the benefits when the process is too automated. For example, the improved Windows Update feature in Windows XP now allows patches and updates to be downloaded automatically, although installation is still at the users discretion. Trojan horses, worms, and other malicious code forms have proven to be incredibly successful at paralyzing e-mail systems and Internet providers. It is therefore only logical to conceive of ways to use them for productive purposes, much as the Bible exhorts its readers to beat their swords into plowshares and their spears into pruning hooks. Granted, it would be wonderful if IT administrators could distribute patches and software updates to desktops and servers as quickly as an e-mail virus can spread from one machine to the next. But is such a magic wand really a good idea? Well, maybe not exactly. After all, unlike the human immune system, which produces defenses, or antibodies, automatically, the computer must wait for a human to analyze samples of a computer virus, prepare antidotes and vaccines for that specific situation, and only then apply the cure. This observation alone would seem to discredit the idea of a “digital immune system” that the security community has tossed around during the past few years, but theres an even more important point to consider. Similar to the way that autoimmune diseases turn the body s own defenses against itself, so could one turn a viruslike software delivery system against its own computers. Although it would be difficult to monkey with the digital certificates that would conceivably be used to identify trusted patches, its not impossible to subvert the certificate issuing system.Viruses, worms, and Trojan horses are programs created by hackers that use the Internet to infect vulnerable computers. Viruses and worms can replicate themselves from computer to computer, while Trojan horses enter a computer by hiding inside an apparently legitimate program, such as a screen saver. Destructive viruses, worms, and Trojan horses can erase information from your hard disk or completely disable your computer. Others don't cause direct damage, but worsen your computer's performance and stability.Antivirus programs scan email and other files on your computer for viruses, worms, and Trojan horses. If one is found, the antivirus program either quarantines (isolates) it or deletes it entirely before it damages your computer and files.Because new viruses are identified every day, it's important to select an antivirus program with an automatic update capability. When the antivirus software is updated, it adds new viruses to its list of viruses to check for, helping to protect your computer from new attacks. If the list of viruses is out of date, your computer is vulnerable to new threats. Updates usually require an annual subscription fee. Keep the subscription current to receive regular updates.Tips for using email and the web safely:(1)Use caution when opening email attachments. Email attachments (files attached to email messages) are a primary source of virus infection. Never open an attachment from someone you don't know. If you know the sender but were not expecting an attachment, verify that the sender actually sent the attachment before you open it. See when to trust an email message and Avoiding email viruses.(2)Guard your personal information carefully. If a website asks for a credit card number, bank information, or other personal information, make sure that you trust the website and verify that its transaction system is secure. (3)Use the Phishing Filter in Internet Explorer. Phishing is the practice of creating fraudulent email messages and websites in order to trick computer users into revealing personal or financial information. The fraudulent email message or website appears to be from a trusted source, su