What can computer viruses be classified according to their transmission media?

Classified according to the propagation medium of computer viruses, they can be divided into stand-alone viruses and network viruses. Stand-alone viruses are the former DOS viruses, Windows viruses and macro viruses that can run under multiple operating systems; network viruses are computer viruses that infect executable files through computer networks.

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Computer Virus (Computer Virus) is a program created by the programmer A set of computer instructions or program code that is inserted to destroy computer functions or data, can affect the use of the computer, and can replicate itself.

Computer viruses are artificially created, destructive, contagious and latent programs that damage computer information or systems. It does not exist independently, but is hidden in other executable programs. When a computer is infected with a virus, it may affect the running speed of the machine at first, or crash and damage the system at worst. Therefore, the virus brings great losses to the user. Under normal circumstances, we call this destructive program a computer virus.

Classified according to the propagation medium of computer viruses, they can be divided into stand-alone viruses and network viruses.

Stand-alone virus

Stand-alone virus is the former DOS virus, Windows virus and macro virus that can run under multiple operating systems.

DOS viruses are virus programs written on MS-DOS and its compatible operating systems, such as the previously famous "Black Friday", "DIR" and other viruses. They run on the DOS platform. Due to Win3.x /Win9x still uses or contains the DOS kernel, so this type of virus can still attack Windows systems, occur on Windows platforms, and infect files on the hard disk.

Windows viruses are pure 32-bit virus programs written on Win3. , infect system files and executable files, destroy user data, and even erase the motherboard BIOS, causing damage to the motherboard. As we all know, the number of viruses on DOS and Win3.x/Win9x is staggering, while the number of viruses on Windows NT is much less.

Macro virus is a virus written using Office's unique "Macro". It specifically attacks Microsoft Office series Word and Excel files. This virus can not only run in Windows environment, but also in Microsoft Office software on OS/2 or MAC OS, because Office software has multiple versions of For Windows, For OS/2 or For MAC OS, and all versions The definition of "macro" is the same

So as long as you open an Office document on these operating systems, macro viruses will start to attack, infecting other Office documents, changing file attributes, and even deleting files, such as "July Killer" The macro virus will attack on any day in July. When the attack occurs, the "Awakening of the World" dialog box will pop up, asking the user to choose "OK" or "Cancel". If "Cancel" is pressed, it will be added to autoexec.bat A command to delete the C drive will delete all the data on the C drive when the computer is restarted.

How to prevent stand-alone viruses?

To prevent stand-alone viruses, you should first consider that each anti-virus product has its limitations, so it is best to prepare several sets of anti-virus software and use them for cross-antivirus. The anti-virus software must be upgraded in time; Regularly check the hard disk with anti-virus software. If you are using Win9x (CIH virus does not work on Windows NT and Windows 2000), you must check whether there is CIH virus before the 26th of each month, or skip the system date on the 26th; It is best to install real-time virus monitoring software in the system (generally included with anti-virus software); all CDs and floppy disks that are to be used on the computer must be checked for viruses before they can be used; use Ghost software to back up the system partition into a file and store it in other partitions Once the system is damaged by a virus, it can be restored in a few minutes, but the hard drive must be disinfected before backing up; it is best to divide the hard drive into multiple logical drives, such as C, D, and E. Each drive is preferably in FAT32 format. As the system disk, the C drive should of course have a larger capacity. The C drive is preferably in FAT32 format and the capacity should be greater than 2G

. The advantage of this setting is that it will help improve the system running speed. In addition, if the C drive is CIH If the virus destroys it, as long as it is in FAT32 format and the capacity is greater than 2G, 98% of the data on the C drive can be recovered using general anti-virus software. There are at least 9 variants of the CIH virus, of which V1.2 and V1.3 occur on April 26, V1.4 occurs on the 26th of each month, and some versions occur on June 26.

Network virus

Network virus: A computer virus that infects executable files through a computer network.

Broadly speaking, viruses that can spread through the network and damage certain network components (servers, clients, switching and routing equipment) are network viruses. In a narrow sense, viruses that are limited to the scope of the network are network viruses, that is, network viruses should make full use of network protocols and network architecture as their propagation channels or mechanisms. At the same time, the damage of network viruses should also be targeted at the network.

Features

(1) Infection speed is extremely fast

Under stand-alone operation conditions, the virus will only infect one computer to another through a floppy disk, and can spread rapidly throughout the entire network system through the network communication platform. Combined with the relevant measurement results, under normal operation of the PC network, if a virus exists on a workstation, it will infect hundreds of computer devices in just ten minutes.

(2) Extremely wide spread

In a network environment, the virus spreads very quickly and in a very wide range, and will infect all computers within the LAN within a short period of time. , or the virus can be quickly spread thousands of miles away in a short period of time through remote workstations.

(3) Diversified forms of transmission

For computer network systems, viruses are mainly spread through the basic path of "workstation-server workstation". However, virus transmission forms are diverse.

(4) Unable to completely remove

If the virus exists on a single machine, you can delete the virus-carrying files or low-level format the hard drive to completely remove the virus. If the virus exists on the entire network If one workstation in the environment cannot be thoroughly disinfected, it will infect devices in the entire network system. It is also possible that a workstation has just been cleared and is instantly infected by another workstation carrying a virus. In response to such problems, just carrying out corresponding virus scanning and removal on the workstation will not be able to completely solve and eliminate the harm caused by the virus to the entire network system.

Prevention principles and strategies

(1) Strengthen network users’ security awareness

Network viruses will exist in documents, and computer users need to strengthen themselves Be aware of security precautions and refrain from clicking and downloading unfamiliar documents at will, thereby reducing the chance of your computer being infected with network viruses. In addition, when browsing the Internet, you should not click on unfamiliar web pages easily, mainly because there may be malicious program codes in the web pages and pop-up windows. Therefore, web viruses are widely spread and highly destructive network virus programs. Computer users need to strengthen their awareness of network security and virus prevention, strictly regulate their network behavior, and refuse to browse illegal websites to avoid losses and prevent their computers from being damaged. Invasion of network viruses.

(2) Timely update the computer system

The computer will regularly detect its own deficiencies and vulnerabilities and release system patches. Computer network users need to download and install these patches in a timely manner. Prevent network viruses from invading computers through system vulnerabilities, causing incalculable losses. Computer users need to update and upgrade the system in a timely manner to maintain computer security. In addition, close unused computer ports and promptly upgrade the anti-virus software installed on the system. Use these anti-virus software to effectively monitor network viruses and effectively prevent viruses.

(3) Scientific installation of firewall

Installing a firewall at the internal and external network interfaces of the computer network is also an important measure to maintain computer security. The firewall can effectively isolate the internal network and the external network, and effectively improve the computer Network security. If a network virus program wants to attack a computer, the virus has to first avoid and destroy the firewall to prevent computer users from being attacked. The firewall activation levels are different, and computer users need to choose the corresponding level independently.

(4) Effectively install anti-virus software

Currently anti-virus software is a relatively common method of detecting and killing network viruses, but many users do not correctly understand the role of anti-virus software at the beginning. With the continuous emergence of network viruses, people have begun to realize the importance of anti-virus software, and the improvement and improvement of anti-virus software itself have also made people better accept anti-virus software. Current anti-virus software can monitor computers around the clock and detect network viruses in real time. Moreover, timely updates of anti-virus software and virus databases can effectively detect and kill new network viruses, and their adaptability is relatively strong. If you use anti-virus software for a long time, you can find that anti-virus software can effectively detect and kill network viruses. At the same time, anti-virus software does not occupy too many system resources. Sometimes the computer runs slowly because the anti-virus software is filtering network viruses. In addition, anti-virus software is also more convenient to use. Even if the computer is infected, you can save yourself in a short time.

(5) Back up data files

If a network virus invades the computer, it will cause the computer system to be paralyzed, so computer users need to back up important data in the computer during daily use. With files, this method reduces the losses caused by network viruses to computer users.

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