Computer Virus: Definition, Types, and Examples

Definition of Computer Virus

Computer viruses are almost like flu viruses, they are designed to spread from one host to another host. And they have the ability to replicate themselves every time period. But computer viruses cannot reproduce without host cells, it means that computer viruses cannot reproduce and spread without program such as files or documents.

And in technical terms, computer viruses are a type of malicious code or program that written to change the way computers operate and are designed to spread from one computer to another. Computer Viruses operate by inserting or attaching themselves to legitimate programs or documents that support macros to execute the code. In the process the virus has the potential to cause unexpected or destructive effects, such as damaging system software by damaging or destroying data.

How Computer Virus Attack

After the computer virus has successfully attached to a program, file, or document, the virus will be inactive until a situation causes the computer or device to execute the code. In order for a virus to infect your computer, you must run an infected program, which in turn causes the virus code to run. This means that the virus can remain inactive on your computer, without showing main songs or symptoms.

However, once the virus starts infecting your computer, it can also infect other computers in a network that is connected to your computer. Computer viruses can do various things on your computer without your knowledge, such as stealing passwords or data, recording key presses, corrupting files, spamming your email contacts, and even taking over machines. These are just a few of the destructive and annoying things that viruses can do.

While some computer viruses can play around in intentions and effects, others can have profound and destructive effects, such as deleting data or causing permanent damage to your hard disk, and worst of all, some are even designed taking into account financial benefits.
 Computer Virus: Definition, Types, and Examples

How Computer Viruses Spread

In a world that is constantly connected today, you can contract a computer virus in many ways, some more clearly than others. Viruses can be disseminated via e-mail attachments and text messages, Internet file downloads that contan virus, social media fraud links, and even your mobile devices and smartphones can be infected with cellular viruses through shady Application downloads that contain virus. Viruses can hide it as an attachment of content that can be shared socially such as funny pictures, greeting cards, or audio and video files.

To avoid contact with computer viruses, it is important to be careful when surfing the web, downloading files, and opening links or attachments. As a best practice, never download text or email attachments that you don't expect, or files from websites that you don't trust.

How to Protect Against Computer Viruses

As you can see, like a malignant flu virus, a computer virus is something you want to avoid. The terms viruses and malware are often used interchangeably. However, viruses are one of many types of malware, and are only one aspect of the overall threat landscape.

Therefore, traditional antivirus software or old versions of antivirus will not be able to fully protect you from all threats. Because hackers also always create viruses that are more dangerous and powerful to be able to break into current protection systems.

Instead, look at comprehensive security software like these Antivirus. With technology from patented antivirus that works together to outsmart online threats, scan your system for viruses, and run automatic silent updates continuously, antiviruses can protect your device from existing threats.

If the virus enters through our watch during your subscription period, the antivirus support experts will do anything to help fix the problem at no additional cost. That is the guarantee and peace of mind that you only get with the Promise of Anti-Virus Protection. There are free or paid security software services that offer this kind of guarantee.

To learn more about antivirus, you can visit our article about the complete definition, type, and example of an antivirus. So if you really understand the process or performance of an antivirus, you can determine which antivirus you think has the best performance.

And we have several antivirus references that arefree and without ads, even though this antivirus is free, but it is so powerful to protect your device from various virus attacks.

Types of Computer Virus

Types of Computer Virus
What is a computer virus and types of virus? If we talk about computer security, computer viruses are the main threat. This viruses can destroy just one program or all computer systems. The first virus was created in the 1970s and called the Creeper virus, affecting computers on the ARPANET. In 1981, the first hacker-made virus appeared and spread through Apple's floppy drive.

According to the Information Technology Promotion Agency, the number of viruses swelled to 52,151 in 2004. However, due to certain programs that completely eliminate the virus, the number dropped to around 14,000 in 2010.

What is computer virus and its types? 57% of the threats that affect the security of your computer are viruses. There are many computer virus names like computer Trojan, adware, computer worm, and malware, among others. Now, the virus is still widespread, affecting PC performance. Viruses are also hacking tools to get unauthorized access to your system and steal personal information. It is important for you to know the various types of viruses that affect your computer.

Computer Viruses List

1. Resident Virus

Resident viruses live in your RAM. This can interfere with normal system operations which can cause file and program corruption. The most popular examples of resident viruses are Meve, MrKlunky, Randex, and CMJ.

2. Multipartite Virus

This type of virus can easily spread on your computer system. This is very contagious, takes illegal actions in your operating system, in folders, and other programs on the computer. They have the ability to infect executable files and boot sectors.

3. Direct Action Virus

Virus actions directly attack certain types of files, usually files with extension .exe. The main purpose of this computer virus is to replicate and infect files in your folder, so that your files can become numerous, and can damage your files.  On lighter notes, they usually don't delete files or affect PC performance and speed. It can be easily deleted by an antivirus program.

4. Browser Hijacker

This type of virus infects your web browser which will take you to various websites. Usually, if you enter a domain name in the internet address bar, the browser hijacker will open up some fake websites that can harm your computer. But don't worry, currently most trusted browsers have already provided built-in features that are able to block it

5. Overwrite Virus

From its own name, this virus overwrites the content of the file, losing its original content. It infects folders, files, and even programs. To delete this virus, you must also get rid of your files. Therefore, it is important to back up your data.

6. Web Scripting Virus

This virus lives on links, advertisements, placement of images, videos, and layout of certain websites. This can carry malicious code where when you click, the virus will be automatically downloaded or will direct you to a malicious website that contain viruses.

7. Boot Sector Virus

The boot sector virus affects the floppy disk. They appear when the floppy disk is important in booting the computer. Even though they are not very common today, it still causes other computer units, especially those that are outdated. Some examples include Polyboot.B and AntiEXE.

8. Macro Virus

Macro viruses target applications and software that use macro programming code. This virus can carry out a series of operations that affect the performance of a program or software. Some examples of macro viruses are Relax, Melissa.A, O97M / Y2K, and Bablas.

9. Directory Virus

Directory viruses change the file path. When you run programs and software infected with a virus directory, the virus program also runs in the background. Furthermore, it may be difficult for you to find genuine applications or software that have been infected with a virus directory.

10. Polymorphic Virus

Polymorphic viruses use special coding or encryption methods each time they infect a system. With this, antivirus software is difficult to find and then uses signature search. They are also able to replicate easily. Polymorphic viruses include Bug Satan, Elkern, Tuareg, and Marburg.

11. File Infector Virus

This virus also infects executable files or programs. When you run these programs, activated file infector viruses can slow down the program and produce other damaging effects. A large number of viruses are included in this category.

12. Encrypted Virus

This type of computer virus uses encrypted malicious codes which make antivirus software hard to detect them. They can be detected when they decrypt themselves during replication. Although they don't delete files or folders, they can affect PC performance badly.

13. Companion Virus

This is a type of virus that does not survive without an existing file or folder. To do damage, a file or folder accompanied by a companion virus must be opened or executed. Some examples of companion viruses include Asimov.1539, Terrax.1069, and Stator.

 14. Network Virus

Basically, this type of virus spreads through the Local Network Area (LAN) and via the internet. This virus replicates through shared resources, including drives and folders. When network viruses enter the computer, they search for their potential prey. Malicious network viruses include Nimda and SQLSlammer.

15. Nonresident Virus

Non-resident viruses is one type of computer viruses that replicate through modules. When the module in this virus is executed, it will find one or more files as targets to be executed.

16. Stealth Virus

Stealth viruses do some trick on antivirus software by looking like they are real files or programs and by intercepting requests to the OS. Some antivirus software cannot detect them. Sometimes, it temporarily deletes itself from the system without deletion.

17. Sparse Infector

Sparse Infectors is one of the type of computer viruses that use different techniques to minimize detection. They are "occasional" infecting viruses. For example, they might only want to infect a program every ten executions. Because of their occasional infectors, antivirus software is difficult to detect them.

18. Spacefiller Virus

Also known as a "cavity" virus, spacefiller attaches itself to files and can change the start of the program or change the encrypted code. They also apply stealth techniques so that users cannot determine the increase in the file code. The most popular Spacefiller is the Lehigh virus.

19. FAT Virus

Basically, this type of computer virus damages the file allocation system where information about files, including locations, exists.

20. ILOVEYOU Virus

The ILOVEYOU virus is one kind of computer virus or worm. This virus spread via email with a subject line that said "I love you", and it attack firstly in 2000. And ILOVEYOU virus is one of the most famous and worst computer viruses of all time.

21. Computer Worm

What is a computer worm? Computer worms are one types of malware that spread copies of themselves from one computer to another computer. Worms can replicate themselves without human interaction, and they don't need to attach themselves to a software program to cause damage.

22. Other Virus

Other threats are not technically referred to as "viruses", but they also have the same damaging effects as viruses. This includes adware, malware, Trojans, and ransomware.

To prevent this virus from affecting your computer, you should install at least 1 of the best and most competitive antivirus software that can detect, block, and eliminate all types of viruses from your device.

Examples of Computer Virus

Examples of Computer Virus
Computer viruses generally use some cheat on hosts or other types of computers to reproduce copies of invading organisms. They spread from computer to computer through electronic bulletin boards, telecommunications systems and shared diskettes. Viruses are created by human programmers, for pleasure or envy, but once they begin to spread they take their own lives, creating disturbances, anxieties and paranoia behind them.

If a virus is found on one PC, the PC must be isolated immediately. Viruses can be removed by giving antidotes by studying viruses. The machine must be used only after the virus has been removed.


Viruses are defined as programs that are included in other programs. It is activated by the host program. It replicates itself and spreads to other people via floppy transfers. Viruses infect data or programs every time a user runs an infected program and the virus takes advantage and replicates itself.

There are two types of 'parasitic' computer viruses and 'boot' viruses.

Parasitic viruses stick to other programs and are activated when the host program is run. Trying to connect to more programs so that the opportunity to be activated more. This spreads to other computers when the affected program is copied. 'Jerusalem' and 'Datacrime' are examples of parasitic viruses.

Boot Virus or boot sector virus is computer virus that is designed to enter the floppy disk boot sector. It works by replacing the first sector on the disk with a part of itself. It hides the rest of itself elsewhere on the disk, with the first sector copy. This boot sector virus is loaded by a built-in computer start-up program when the engine is turned on. The virus loads, installs itself, hides the rest and then loads the original program. On hard disks, viruses can occupy the DOS boot sector or the master boot sector.

 Reported Viruses

C-Brain: Amjad and Basit, two Pakistani brothers, developed this software in January 1986 to prevent people from buying illegal software at low prices. This is the most famous virus ever discovered and has a record of damaging several million personal computers. This is designed to remain in the boot disk sector or close to zero sector. The virus enters machine memory after the PC is booted with an infected diskette.

Macmag: This virus only attacks Apple Macintosh computers. Not much damage was reported due to this virus. This was not noticed on compatible IBM PCs. It displays a message of peace on the monitor and suicide.

Cascade: This virus attacks IBM PCs and is compatible. The letters on the screen can be seen vertically down to the bottom of the screen after the virus picks them up in alphabetical order. This is a kind of parasitic virus. It attaches to other programs and is activated when the host program is run. It will be copied to another PC when the program is copied.

Jerusalem: This virus was found in 1987 at Hebrew University, Jerusalem. And this virus was designed to be active only on Friday, January 13 and deleted all files executed on that day. This virus infects COM and EXE files. This is similar to the Cascade virus because it is parasitic. This virus attaches to COM and EXE files to damage the data.

Daracrime / Columbus or October 13 virus: This virus is similar to Jerusalem and was programmed to attack on October 13, 1989. Tracking zero computer hard disks is destroyed and the contents of the disk cannot be read. 

This virus are able to enters COM and EXE files and damages your hard disk. The antidote called 'Vchecker' was developed by the American Computer Society. Fortunately the virus was discovered in March 1989 and the damage reported after October 13 was very small.

Bombs: These are also known as 'Logic Bombs' and 'Time Bombs'. An event that triggers a routine in a program that causes a crash program is defined as a 'bomb'. In general, a 'bomb' is software that is included in a program by someone who works in a company.


That was the explanation of definitions, types, and examples of computer viruses. However, the virus mentioned above does not only attack the computer, but your device such as smartphone can also be attacked by these viruses.

So from now on you should start checking your device now, whether your device is infiltrated by a virus or not. Because like what you have read before, the effects of computer viruses are very dangerous.

So pay attention to whether your device seems to have strange symptoms like it feels very slow or the application that is run often crashes suddenly, because that could be one sign that your device is infected with a computer virus. And it would be better if you read the full explanation of the symptoms of the virus, so you can protect your device immediately.

And if you realize that your device has a virus, then your device suddenly experiences a lot of problems, you can try to read these tips from us to fix problems on your device.

And hopefully what numbones.com share could be useful for you, and can protect you from all virus attacks that might attack  your device. Thank You!

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