A computer virus is a program, an executable code. Just like biological viruses, computer viruses have unique replication capabilities. Computer viruses spread quickly and are usually difficult to eradicate. They can attach themselves to various types of files. When files are copied or transferred from one user to another, they will spread with the files.
In addition to replication ability, some computer viruses have other common features: contaminated programs can spread virus vectors. When you see that virus carriers only appear in words and images, they may have destroyed files, reformatted your hard disk or caused other types of disasters. If the virus is not parasitic on the infected program, it will still bring you trouble by occupying storage space and reducing the overall performance of the computer.
The definition of computer virus can be given from different angles. One definition is a program that spreads through media such as disk, tape and network and can "infect" other programs. The other is a latent, infectious and destructive program, which can replicate itself and exist with the help of some kind of carrier. Another definition is artificial program, which is hidden or parasitic in storage media (such as disk and memory) or programs through different channels. When a certain condition or time is ripe, it will copy and spread itself, destroy computer resources through different programs and so on. In a sense, these statements borrowed the concept of biological virus. Computer viruses are similar to biological viruses in that they are both "pathogens" that can invade computer systems and networks and endanger normal work. It can cause all kinds of damage to the computer system, and at the same time it can replicate itself, which is contagious. Therefore, computer virus is a set of programs or instructions, which can lurk in computer storage media (or programs) in some way and be activated when certain conditions are met, thus destroying computer resources.
Different from biological viruses, almost all computer viruses are deliberately created by human beings. Once they spread, sometimes even editors can't control themselves. It is no longer a simple academic computer problem, but a serious social problem.
A few years ago, most types of viruses were mainly transmitted through floppy disks, but the Internet introduced a new virus transmission mechanism. As e-mail is now used as an important enterprise communication tool, viruses spread faster than ever before. The virus attached to e-mail can infect the whole enterprise in just a few minutes, causing millions of dollars in production losses and virus removal costs to the company every year.
The virus will not disappear soon at any time in the future. According to the statistics released by the National Computer Security Association, there are more than 10000 viruses identified at present, and 200 new viruses are still being produced every month. To be on the safe side, we say that most organizations must deal with sudden virus outbreaks on a regular basis. Any organization that uses multiple computers is not immune from viruses.
Under what circumstances did the computer virus appear?
The emergence of computer virus is the inevitable product of the development of computer technology and the development of computer-centered social informatization. Its background is:
(1) Computer virus is a new derivative form of computer crime.
Computer virus is a high-tech crime, which is instantaneous, dynamic and random. It is difficult to obtain evidence, with little risk and great harm, thus stimulating criminal awareness and criminal activities. It is a manifestation of some people's mischief and revenge in the field of computer application.
(2) The fragility of computer software and hardware products is the fundamental technical reason.
Computers are electronic products. Data from the input, storage, processing, output and other links, easy to go astray, tamper, loss, fraud and destruction; Programs are easy to be deleted and rewritten; The manual method of computer software design is inefficient and the production cycle is long; So far, people have no way to know in advance whether a program has errors, and they can only find and modify errors during the running process, and they don't know how many errors and defects are hidden. These vulnerabilities facilitate the invasion of viruses.
(3) The popularization and application of microcomputers is a necessary environment for the generation of computer viruses.
1983165438+1October 3rd, American computer experts first put forward the concept of computer virus and verified it. A few years ago, computer viruses spread rapidly, and only in recent years did they spread to China. These years are the climax of the popularization and application of microcomputers in China. With the widespread popularity of microcomputers, the operating system is simple and clear, the transparency of software and hardware is high, and there are basically no security measures. More and more users can thoroughly understand its internal structure, and its shortcomings and loopholes are becoming clearer, so they can make different choices for different purposes. At present, all kinds of viruses are widely popular in IBM PC system and its compatible computers, which illustrates this problem.
What are the sources of computer viruses?
(1) Viruses created by pranks and fun of computer users and amateurs, such as benign viruses like Diandian.
(2) Retaliatory punishment measures taken by software companies and users to protect their software from illegal copying. Because they found that locking software might as well hide the virus inside, which further contributed to the spread of various viruses.
(3) Viruses created to attack and destroy computer information systems and computer systems are deliberate sabotage. For example, the Jewish virus at the end of Hebrew University in Jerusalem 1987 was deliberately created when employees were frustrated or dismissed. It is highly targeted and destructive, and it is produced from the inside, which is difficult to prevent.
(4) The program designed for research or beneficial purposes is out of control or produces unexpected effects for some reason.
References:
/computer/theory /2 12 10.htm
There are many more:/computer/see for yourself.