Methods of transmission: 1. Through floppy disks, file-type diseases can be spread through floppy disks; 2. Through optical discs, because optical discs have large capacity and can store massive executable files; 3. Through network transmission, this method spreads It is extremely fast and can be transmitted to all machines on the network in a very short time. Hazards: 1. Attack the hard disk's main boot sector, Boot sector, FAT table, and document directory, causing information on the disk to be lost; 2. Delete executable documents or data files on the floppy disk, hard disk, or network, causing the document to be lost; 3. , occupy disk space; 4. Modify or destroy the data in the document, causing the content to change.
The operating environment of this tutorial: Windows 7 system, Dell G3 computer.
Computer virus (Computer Virus) refers to a set of computer instructions or program codes inserted by the programmer into a computer program that destroy computer functions or destroy data, affect the normal use of the computer, and are capable of self-replication.
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.
The main transmission route of computer viruses
1. Floppy disk: through the use of floppy disks infected by the outside world.
As the most commonly used exchange medium, floppy disks played a huge role in the spread of viruses in the early days of computer application. Because computer applications were relatively simple at that time, executable files and data file systems were small. , many executable files are installed through floppy disks copying each other, so that viruses can spread file-type viruses through floppy disks: In addition, when the floppy disk is cataloged or the machine is booted, the boot area virus will infect each other in the floppy disk and hard disk area. Therefore, floppy disks have also become the main parasitic "breeding ground" for computer viruses.
2. CD
Because the CD has a large capacity and stores a large number of executable files, a large number of viruses may hide in the CD. For read-only CDs, Writing operations cannot be performed, so the virus on the disc cannot be removed. In the process of producing illegally pirated software for profit, it is impossible to take special responsibility for virus protection, and there will never be truly reliable and feasible technical guarantees to avoid the introduction, infection, epidemic and spread of viruses. Currently, the proliferation of pirated CDs has brought great convenience to the spread of viruses.
3. Hard disk
Because the hard disk with the virus is used or repaired locally or moved to other places, the clean floppy disk will be infected and then spread.
4. U disk
U disk has the characteristics of small size, portability, large storage capacity, and low price, but at the same time, viruses can also be transmitted to the computer through the U disk.
5. BBS
Electronic bulletin board BBS is very popular among users because it is easy to get on the site and requires low investment. BBS is a communication site voluntarily organized by computer enthusiasts. Users can exchange files including free software, games, and self-written programs on BBS. Since BBS sites generally do not have strict security management and no restrictions, this provides some virus program writers with a place to spread viruses. BBS stations in various cities are transmitted through central stations, with a wide spread area. With the popularity of BBS in China, new media have been added to the spread of viruses.
6. Network
The great progress of modern communication technology has made the space distance no longer far away, and data, files and emails can be conveniently
Transmission is carried out between various network workstations through cables, optical fibers or telephone lines. The distance between workstations can be as short as computers placed side by side, or as long as tens of thousands of kilometers. As the saying goes, "we are as close as we are to each other at the end of the world", but it is also a computer The spread of the virus provides a new "highway". Computer viruses can attach themselves to normal files and spread when you get an infected program from the other side of the network and run it on your computer without any protection. This method of virus infection is very common in countries where computer network connections are widespread. It is no longer a big deal for domestic computers to be infected by an "imported" virus. While our information is internationalizing, our viruses are also internationalizing. A large number of foreign viruses have been introduced into the country along with the Internet.
With the popularity of the Internet, new ways have been added to the spread of viruses, and they will become the first way of spread. The pioneering development of the Internet has made viruses potentially catastrophic, spreading more rapidly and making anti-virus tasks more difficult. The Internet presents two different security threats. One threat comes from file downloads, which may contain viruses when they are browsed or downloaded via FTP. Another threat comes from email. Most Internet mail systems provide the function of transmitting emails with formatted documents between networks. Therefore, virus-infected documents or files may flood into the corporate network through gateways and mail servers. The ease and openness of using the Internet make this threat increasingly serious.
Currently, the latest trend of viruses on the Internet is:
1) Anonymous personal web pages created by criminals or bad guys directly provide the ability to download a large number of live virus samples. Convenient way.
2) Virus sample providing institutions for academic research can also become tools for people with ulterior motives.
3) Academic electronic papers, journals, magazines and related online academic exchange activities that are dedicated to virus production research and discussion, such as the Virus Production Association, are made possible by anonymous login on the Internet Annual meetings, etc., may become targets and targets for any new virus creators at home and abroad who want to become new virus makers to learn, learn from, steal, and plagiarize.
4) There are a large number of virus creation tools, wizards, programs, etc. scattered on the website, making it possible for people without programming experience and foundation to create new viruses.
5) New technologies and new viruses make almost everyone unintentionally become the carrier or spreader of the virus without knowing it.
Main hazards of computer viruses
1. Attack hard disk master boot sector, Boot sector, FAT table , document directory, causing the information on the disk to be lost.
2. Delete executable documents or data documents on the floppy disk, hard disk or network, causing the documents to be lost.
3. Occupies disk space.
4. Modify or destroy the data in the document to change the content.
5. Seize system resources to reduce memory.
6. It takes up CPU running time and reduces running efficiency.
7. Format the entire disk or sector.
8. Destroy the BIOS content on the computer motherboard and make the computer unable to work.
9. Destroy the normal display of the screen and interfere with the user's operation.
10. Destroy the keyboard input program and cause errors in the user's normal input.
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