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2 Characteristics of computer network attacks Computer network attacks have the following characteristics: â‘ huge losses; â‘¡ threat to society and national security; â‘¢ diverse methods, concealed means; â‘£ mainly software attacks.
3 Main factors affecting network security ①Information leakage. ②The information has been tampered with. ③Transmit illegal information flow. ④Incorrect use of network resources. ⑤Illegal use of network resources. ⑥Environmental impact. ⑦ Software vulnerability. ⑧Artificial safety factors.
4 Security flaws and causes in computer networks 4.1 Vulnerability of TCP / IP. The foundation of the Internet is the TCP / IP protocol. But the protocol does not consider much about the security of the network. And, because the TCP / IP protocol is published to the public, if people are familiar with TCP / IP, they can use its security flaws to carry out network attacks.
4.2 The insecurity of the network structure. The Internet is a network technology. It is a huge network connected by countless local area networks. When people use a host to communicate with a host on another local area network, under normal circumstances, the data streams transmitted between them must be repeatedly forwarded by many machines. If an attacker uses a host on the user's data stream transmission path , He can hijack the user's data packets.
4.3 Easy to be tapped. Since most data streams on the Internet are not encrypted, people can easily eavesdrop on online e-mails, passwords, and transmitted files using tools that are provided free of charge on the Internet.
4.4 Lack of security awareness. Although many security protection barriers are set up in the network, people generally lack security awareness, so that these protection measures are virtually useless. For example, in order to avoid the additional authentication of the firewall proxy server, a direct PPP connection is made to avoid the firewall protection.
5 Common cyber attacks 5.1 Trojan horses. The Trojan horse program can directly invade the user's computer and be destroyed. It is often disguised as a tool program or game, etc. to induce the user to open the email attachment with the Trojan horse program or download it directly from the Internet. Once the user opens the attachment of these emails or After executing these programs, it will hide a program in the computer system that can be executed quietly when Windows starts. When you connect to the Internet, this program will notify the attacker to report your IP address and pre-set port. After receiving this information, the attacker can then use this latent program to modify the parameter settings of your computer, copy files, peek at the contents of your entire hard disk, etc. to control your computer. purpose.
5.2 WWW deception technology. Online users can use IE and other browsers to access various WEB sites, but the average user may not think of these problems: the web page being accessed has been tampered with by hackers. For example, the hacker rewrites the URL of the web page that the user wants to browse to point to the hacker's own server. When the user browses the target web page, he actually sends a request to the hacker server, so the hacker can achieve the purpose of deception.
5.3 Mail bomb. E-mail is a widely used communication method on the Internet. Attackers can use some mail bomb software or CGI programs to send a large amount of spam to the destination mailbox, thereby making the destination mailbox burst and unusable. When the sending traffic of spam is particularly large, it may cause the mail system to respond slowly to normal work, or even paralyze it. Compared with other attack methods, this attack method has the advantages of simplicity and quick results.
5.4 Overload attack. Overload attack is that the attacker sends a lot of useless requests through the server for a long time, so that the attacked server has been busy all the time, which can not meet the requests of other users. One of the methods most used by attackers in overload attacks is process attack, which artificially increases the workload of the CPU by a large amount, consumes the CPU's working time, and keeps other users in a waiting state.
5.5 Network monitoring. Network monitoring is a working mode of the host. In this mode, the host can receive all the information transmitted on the same physical channel of this network segment, regardless of the sender and receiver of the information. Because when the system performs password verification, the password entered by the user needs to be transmitted from the user end to the server end, and the attacker can monitor the data between the two ends. At this time, if the information communicated between the two hosts is not encrypted, as long as some network monitoring tools (such as NetXRay for Windows95 / 98 / NT, Sniffit for Linux, Solaries, etc.) can be used to easily intercept information including passwords and account numbers data. Although the user accounts and passwords obtained by network monitoring have certain limitations, the listeners are often able to obtain all user accounts and passwords of the network segment where they are located.
5.6 Security vulnerability attack. Many systems have bugs in one way or another. Some of them are owned by the operating system or application software itself. Such as buffer overflow attacks. Because many systems do not check the changes between the program and the buffer, they accept data input of any length arbitrarily, put the overflowed data on the stack, and the system executes the command as usual. In this way, as long as the attacker sends a command that exceeds the length of the buffer, the system will enter an unstable state. If the attacker specifically configures a string of characters to be used for the attack, he can even access the root directory and thus have absolute control over the entire network.
6 Preventive countermeasures Based on the above analysis and identification of network attacks, we should carefully formulate targeted strategies. Clarify security targets and set up a strong security guarantee system.
6.1 Improve safety awareness. Don't open unidentified emails and files at will, and don't run programs that are given to you by people you don't know well; try to avoid downloading unknown software and game programs from the Internet; password settings should be mixed with alphanumeric, pure English Or the numbers are easy to exhaust; download and install system patches in a timely manner; do not run hacker programs casually.
6.2 Use anti-virus and anti-black firewall software to treat anti-virus and anti-black as daily tasks. A firewall is a barrier to prevent hackers in the network from accessing an organization's network. It can also be called a threshold for controlling communication in and out of both directions. On the network boundary, the internal and external networks are isolated by the corresponding network communication monitoring system established to prevent the intrusion of external networks.
6.3 Set up a proxy server and hide your IP address to increase vigilance against attacks. It is important to protect your IP address. In fact, even if a Trojan horse program is installed on your machine, the attacker will have no way without your IP address, and the best way to protect the IP address is to set up a proxy server. The proxy server can play the role of an intermediate transfer from the external network to access the internal network. Its function is similar to a data forwarder, which mainly controls which users can access which types of services. When the external network applies for a certain network service to the internal network, the proxy server accepts the application, and then it decides whether to accept the service based on its service type, service content, object being served, time applied by the server, domain name range of the applicant Service, if accepted, it forwards the request to the internal network.
6.4 Regular data backup and analysis of time logs and records. Always perform data backup to prevent important data from being tampered and deleted due to attacks. You should frequently check the firewall logs, intrusion detection logs, and check whether the antivirus software update components are up-to-date.
7 Conclusion Security management has always been one of the weak links of network systems, and users often have quite high requirements for network security, so security management is very important. Network managers must be fully aware of potential security threats and take certain precautionary measures to minimize the consequences of these threats and minimize the danger.
Computer Network Security and Preventive Technology
1 Definition of network security The so-called network security refers to the protection of the hardware, software and data of the network system from accidental factors or malicious attacks that can be destroyed, modified or leaked to ensure that the system is continuous, reliable and normal Network operation without interruption. Common problems affecting network security mainly include viruses, hacker attacks, system vulnerabilities, and data tampering. This requires us to establish a complete network security system to ensure the safe and reliable operation of the network.