The hazards and symptoms of computer viruses

In the early days of computer viruses, when it comes to the harm of computer viruses, they often focus on the direct destruction of the information system, such as formatting the hard disk, deleting file data, etc. This distinguishes between malignant and benign viruses. In fact, these are only part of the virus's misdeeds. With the development of computer applications, people deeply understand that all viruses can cause serious damage to computer information systems.

The main hazards of computer viruses are:

1. The virus stimulates the direct destruction of computer data information. Most viruses directly destroy the important information data of the computer when it is activated. The methods used are formatting the disk, rewriting the file allocation table and directory area, deleting important files or using meaningless. “ Garbage data rewrite files, destroy CMO5 settings. Disk killer virus (D1SK; KILLER), which contains a counter, which is activated within 48 hours after the hard disk is infected. When it is activated, the screen displays "Warning!! Don'tturn; off; power; or; remove; Diskette; while Disk; Killer; is; Prosessing! (Warning! D1SK; KILLER; ll1 is working, don't turn off the power or remove the disk), rewrite the hard drive data. Hard drives destroyed by D1SK KILLER can be repaired with anti-virus software, don't give up easily.

2. Take up disk space and damage information; viruses that are parasitic on disk always take up some disk space illegally. The general encroachment mode of the boot virus is that the virus itself occupies the disk boot sector, and the original boot sector is transferred to other sectors, that is, the boot virus covers a disk sector. The covered sector data is permanently lost and cannot be recovered. The file-type virus uses some DOS functions to infect. These DOS functions can detect the unused space of the disk and write the infected part of the virus to the unused part of the disk. Therefore, in the process of infection, the original data on the disk is generally not destroyed, but the disk space is illegally occupied. Some file-type viruses spread very quickly, infecting a large number of files in a short period of time, and each file is lengthened to varying degrees, resulting in a serious waste of disk space.

3. Seize system resources; except for a small number of viruses such as VIENNA and CASPER, most other viruses are resident in memory under dynamic conditions, which inevitably preempts part of system resources. The basic memory length occupied by a virus is roughly the same as the length of the virus itself. The virus preempts memory, causing memory to decrease and some software cannot run. In addition to occupying memory, the virus also preempts the interrupt and interferes with system operation. Many of the functions of a computer operating system are implemented by interrupt calling techniques. In order to stimulate the virus, the virus always modifies some related interrupt addresses, and adds the virus's "private goods" during the normal interruption process, thereby disturbing the normal operation of the system.

4. Affects the running speed of the computer; after the virus enters the memory, it not only interferes with the system operation, but also affects the speed of the computer. The main performance is as follows: (1) In order to judge the conditions of the infection, the virus must always monitor the working state of the computer, which is normal with respect to the computer. Operating conditions are both redundant and harmful. (2) In order to protect themselves, some viruses not only encrypt the static virus on the disk, but also the dynamic virus after entering the memory is in the encrypted state. Each time the CPU addresses the virus, it runs a decryption program to encrypt the virus. Decrypted into a legitimate CPU command and executed again; and when the virus finishes running, use a program to re-encrypt the virus. This allows the CPU to execute thousands or even thousands of instructions. (3) The virus also needs to insert illegal extra operations when it is infected, especially when the floppy disk is infected, not only the computer speed is obviously slow, but also the normal reading and writing sequence of the floppy disk is disturbed, and the harsh noise is emitted.

5. Computer virus errors and unforeseen hazards A major difference between computer viruses and other computer software is the non-responsibility of viruses. It takes a lot of manpower and material resources to compile a complete computer software. After a long time of debugging, the software can be launched. However, it seems unnecessary for virus compilers to do so and it is not possible to do so. Many computer viruses are thrown out by individuals after they have been hurriedly debugged on a computer. After analyzing a large number of viruses, anti-virus experts found that most viruses have different degrees of errors. Another major source of error viruses is the variant virus. Some beginners do not have the ability to independently compile software, and modify other people's viruses for curiosity or other reasons, causing errors. The consequences of computer virus errors are often unpredictable. Anti-virus workers have pointed out in detail that there are 9 errors in the Black Friday virus and 5 errors in the Ping Pong virus. But people can't spend a lot of time analyzing the tens of thousands of viruses. The spread of a large number of viruses containing unknown errors is unpredictable.

6. The compatibility of computer virus compatibility on system operation is an important indicator of computer software. Software with good compatibility can be run under various computer environments. On the contrary, software with poor compatibility is suitable for running conditions. Type and operating system version, etc. Virus compilers generally do not test viruses in a variety of computer environments, so virus compatibility is poor and often leads to crashes. ;7. Computer viruses cause severe psychological stress to users; according to computer sales department statistics, computer after-sales users suspect that "computers have viruses and consulted about 60% of after-sales service." About 70% of the viruses are detected by the test, and another 30% are only suspected by the user, but the computer does not have a virus. So what is the reason for the user to suspect the virus? Most of them are phenomena such as computer crashes and abnormal software running. These phenomena are indeed most likely caused by computer viruses. But not all, in fact, in the computer work "when abnormal, it is difficult to ask an ordinary user to accurately determine whether it is a virus. Most users take a more convincing attitude towards the virus, which is absolutely necessary to protect computer security. However, it often costs time and money. It’s hard to make up for the damage caused by just suspicion of a virus and formatting the disk. Not only are individual stand-alone users, but in some large-scale network systems, it is inevitable to stop the virus for screening viruses. In short, computer viruses are like the ghosts in the hearts of the majority of computer users, causing tremendous psychological pressure on people, greatly affecting the efficiency of the use of modern computers, and the resulting intangible losses are difficult to estimate.