Abstract: In recent years, computer networks have made rapid development, and network security issues have also become the focus of attention. This paper analyzes the main factors affecting network security, and focuses on several commonly used network information security technologies.

Computer network security refers to the use of network management control and technical measures to ensure the confidentiality, integrity and availability of data are protected in the network environment. Computer network security includes two aspects, namely physical security and logical security. Physical security refers to the physical protection of system equipment and related facilities to prevent damage and loss. Logical security includes the integrity, confidentiality and availability of information.

With the continuous development of computer network, global informatization has become a major trend of human development. However, due to the diversity and interconnection of connection forms, the lack of security mechanism and weak awareness of protection, computer networks are vulnerable to attacks by hackers, malicious software and other improper behaviors. Therefore, the security and confidentiality of network information is a crucial issue.

First, the main factors threatening network security

There are many factors that affect computer network security. The threats to network security mainly come from three aspects: unintentional mistakes, malicious attacks, loopholes in network software systems and "back doors", which can be summarized as follows:

1. Application system and software security vulnerabilities. It is difficult for WEB servers and browsers to guarantee security. At first, people introduced CGI programs to make the homepage alive. However, many people don't know much about this package when writing CGI programs. Most people didn't do the new program, just modified it appropriately. Therefore, many CGI programs inevitably have the same security vulnerabilities. And every operating system or network software can't be perfect, so it is always in a dangerous situation. Once connected to the network, it may become the target of attack.

2. Security policy. Improper security configuration leads to security loopholes, such as incorrect firewall software configuration, which doesn't work at all. Many websites unconsciously expand access rights in firewall configuration, ignoring that these rights may be abused by others. The main purpose of network intrusion is to gain the storage right, writing right and access right to other stored contents of the system, or as a springboard to further enter other systems, or maliciously destroy this system, so that it is destroyed and loses its service ability. For a specific network application, when it is started, a series of security vulnerabilities will be opened, and many applications bundled with this software will also be enabled. Unless the user prohibits the program or configures it correctly, security risks will always exist.

3. Back door and Trojan horse. In computer system, backdoor refers to the access password deliberately set by the software and hardware makers for unauthorized access in the program, but it also poses a potential serious threat to the computer system in the network because of its large storage capacity. Trojan horse is a special backdoor program and a hacker tool based on remote control, which has the characteristics of concealment and unauthorized. If the Trojan server program is installed on the computer, hackers can use the Trojan controller program to enter the computer and control the computer by commanding the server program.

4. virus. At present, the number one enemy of data security is computer virus, which is a set of computer instructions or program codes inserted into a computer program by a compiler, which destroys computer functions or data, affects the normal operation of hardware, and can replicate itself. It has some characteristics of virus, such as spreading, concealment, destructiveness and latency, and some characteristics of itself, such as not using file parasitism (some only exist in memory), causing denial of service to the network, and combining with hacker technology.

5. Hackers. Hackers, usually programmers, have advanced knowledge of operating systems and programming languages, and take advantage of system security loopholes to illegally enter other people's computer systems, which is very harmful. In a sense, hackers do more harm to information security than ordinary computer viruses.

Second, the commonly used network security technology

1. Antivirus software technology. Anti-virus software is the most common software in our computers and the most common security technology solution, because this technology is the simplest to implement, but we all know that the main function of anti-virus software is anti-virus, and its function is limited, which can not fully meet the needs of network security. This method can basically meet the needs of individual users or small enterprises, but if individuals or enterprises have e-commerce needs, they cannot fully meet them. Fortunately, with the continuous development of anti-virus software technology, the mainstream anti-virus software has a good effect on preventing the invasion of hackers such as Trojan horses. Other antivirus software developers also provide software firewalls, which have certain firewall functions and can play the role of hardware firewalls to a certain extent, such as: 360, Jinshan firewall, Norton firewall and so on. 2. Firewall technology. Firewall technology refers to the security application measures to implement access control for internal and external network communication through predefined security policies. Firewalls can be divided into hardware firewalls and software firewalls in terms of implementation. Generally speaking, a hardware firewall is a hardware firewall. By combining hardware and software, the internal and external networks can be isolated. Expensive, but the effect is good, which is difficult for small enterprises and individuals. Software firewall is realized by pure software, and the price is very cheap, but this kind of firewall can only achieve the purpose of restricting some illegal users from accessing the intranet through certain rules. However, the firewall is not as impenetrable as people think. In the past statistics, one-third of network users who were attacked by hackers were protected by firewalls, which means that a series of other measures must be taken to ensure the security of network information, such as encrypting data. It should be noted that the firewall can only resist the intrusion from the external network, but it can't do anything about the security of the enterprise intranet. In order to ensure the security of enterprise internal network, it needs to be effectively controlled and realized.

3. Data encryption technology. The security technologies used in cooperation with firewall include file encryption and digital signature technology, which is one of the main technical means to improve the security and confidentiality of information systems and data and prevent confidential data from being stolen, intercepted or destroyed by the outside. According to different functions, file encryption and digital signature technologies are mainly divided into four technologies: data transmission, data storage, data integrity identification and key management. Data storage encryption technology aims to prevent data loss in storage links, which can be divided into ciphertext storage and access control; The purpose of data transmission encryption technology is to encrypt the data stream in transmission. There are two common methods: line encryption and port encryption. The purpose of data integrity authentication technology is to verify the identity of the personnel involved in the transmission, access and processing of information and related data content, so as to meet the requirements of confidentiality. By comparing and verifying whether the characteristic values input by the object conform to the preset parameters, the system realizes data security protection. Data encryption focuses on the application of keys in many occasions, and key management technology is actually for the convenience of data use. Key management technology includes security measures such as key generation, distribution and storage, replacement and destruction.

Data encryption technology mainly ensures the security and reliability of the network by encrypting the network data, which can effectively prevent the disclosure of confidential information. In addition, it is also widely used in information authentication, digital signature and other technologies to prevent cheating, and plays an extremely important role in the security of information processing systems.

4. Intrusion detection technology. Network intrusion detection technology is also called network real-time monitoring technology. It checks the data flow on the network in real time through hardware or software, and compares it with the intrusion feature database in the system. Once there are signs of being attacked, it immediately responds according to user-defined actions, such as cutting off the network connection, or notifying the firewall system to adjust the access control policy and filter out the invaded packets. Therefore, intrusion detection is a useful supplement to firewall. It can monitor the network without affecting the network performance, thus providing real-time protection against internal attacks, external attacks and misoperation, and greatly improving the security of the network.

5. Network security scanning technology. Network security scanning technology is a security technology to detect security vulnerabilities in remote or local systems. By scanning the network, the network administrator can know the security configuration and running application services of the network, find security vulnerabilities in time and objectively evaluate the network risk level. Using security scanning technology, we can serve the security vulnerabilities of local area network, website, host operating system, system service and firewall system, detect the security vulnerabilities of operating system that may lead to buffer overflow attack or denial of service attack, and also detect whether eavesdropping programs are installed in host system and whether there are security vulnerabilities and configuration errors in firewall system.

Network security is closely related to the development of the network, which is related to the further development and popularization of the Internet. Network security can not only rely on the protection of hardware devices such as antivirus software, firewall and vulnerability detection, but also pay attention to establishing people's awareness of computer security, so as to better protect and truly enjoy the great convenience brought by the network.

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