In this era of technology, the power of computer systems is being harnessed almost all the time. And along with the use of the technology, users are also facing several kinds of breaches that disrupt the regular flow of the computer system. Here in this chapter, we will learn about the reason behind these obstacles and their details.

What Is Meant by the Term Computer Virus?

A computer virus is a malicious program that performs terrible activities on any computer device. Its destructive activity can destroy file systems, steal data, and disrupt services. In addition, the malware writer can install new malware or other actions coded into the system. The destruction of these computer viruses has become a matter of worldwide concern as they cause huge losses of billions of dollars every year.

Symptoms of Computer Virus Infection

There are many symptoms by which we can identify whether our computer system is virus-infected or not. Some of these are:

  • Slow performance of computer system.
  • Showing low storage.
  • Frequent system crashes.
  • Missing files.
  • Automatic creation of multiple folders in the storage drive.
  • Frequent windows pop up.
  • Unfamiliar applications start automatically.

Types of Computer Viruses

Viruses are of different kinds that can affect a user's system in many aspects. Some viruses that can cause damage to computers are as below:

Direct Action

Direct action viruses are file infector virus that acts as self-replicating malware; connected to a workable file. It is a pre-installed virus concealed under the computer memory. It is popularly known as a non-resident virus.

Boot Sector

This boot sector virus came into existence when the floppy disk drive was the primary source for booting the system. These viruses intend to damage the floppy disk by infecting the primary sectors of the floppy disk.

File Infector

File deleting or infecting viruses are those viruses that auto-delete any saved file from the system. Thus whenever the user wants to execute the file, it affects the program. These viruses are loaded with the loading of that particular infected file.


Once this resident virus is installed on the device, the user has a lot of trouble detecting it and getting rid of this virus from the system. This virus is directly installed in the main memory of the system.


These are the types of viruses that affect and spread on the device in many ways. It continuously damages the executable files by performing various malicious activities on the system. These viruses are difficult to remove because they attack actively from both sides. Even if users delete infected files, they remain in the boot sector.


Macro viruses primarily focus commands in MS Word, which has similar programming languages used for MS Office. Therefore, these viruses target programs or software that contain macros.


Polymorphic viruses are tough to remove from the device. This virus changes its code every time a user runs an infected file. These viruses can also reproduce themselves.


These viruses are spread through user email and can infect the content of any application. As the name suggests, it damages files and applications by overwriting them with its code. It also adds extra files to the system to corrupt the files and data.


When rootkit viruses are automatically installed, it opens a gateway for hackers to attack the entire system. Hackers have mainly designed this virus in such a way that it can spoof antivirus software. But these days, rootkit viruses are not very common as it relies on physical storage programs.


Slammer viruses can spread in a fraction of a second, destroying millions of systems. Within minutes, it can spread around the world and infect many computers.

Encrypted Virus

The encrypted virus can be a bit scary as it involves the destruction of encrypting important and intimate documents and files. These viruses generally do not change or delete the files saved on the system but alter the performance of that system to a great extent.


Though Creeper viruses are not dreadful viruses, they can self replicate. In this era of technology, it is the first virus ever spread that besmirch up the connected computer screens, auto displaying the message - "I'm the creeper, catch me if you can."

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