What is a Computer Virus?

A computer virus or its variants affect our technological infrastructure in the digital age. These are a persistent threat that can harm our devices. We must know the nature and various forms of these malicious programs. Moreover, we must take precautions on how the virus spreads and how to protect our digital lives.

In this article, we will look at what a computer virus is and what its types are. We will examine these malicious files in-depth and discuss their infection methods. We will also cover how we analyze or prevent them, as well as their historical context.

Computer Virus Definition and Types

What is a Computer Virus? What are the Types of Viruses?

A computer virus is a nasty program that can sneak into a device and make it delete or mess up the information saved on the hard drive.

We define a computer virus as a program that reproduces itself. Additionally, it interferes with the computer hardware or operating system. Antivirus programs can recognize and remove viruses. They developed this software to ensure the proliferation and spread of viruses.

Before a computer virus can work, it must work. That is, your device loads the virus into memory and then follows the instructions.

We know these instructions are for active virus installation. Active loading modifies and corrupts data files. It also causes malfunctions in the operating system by issuing a specific message. There are other malicious programs similar to viruses. However, these do not meet the requirements for self-replication or detection evasion.

We divide these malicious programs into five categories. These;

The Trojan Horse appears to be a harmless program. However, running such a file is very harmful. Running such a file can cause great harm because the logic bomb activates when it meets a specific condition. The worm slows down our operations by occupying the computer memory.

What is Virus History?

In 1949, mathematician John von Neumann introduced the theoretical possibility of duplicating a program. They tested this theory at Bell Laboratories in the 1950s. Later, they developed a game called Core Wars. Players created programs that attacked the opponent’s system.

In 1983, Fred Cohen coined the term virus. The first Trojan horse appeared in 1985. The virus called Brain spread in 1986. In 1988, Stone and the Internet worm emerged. The following year, in 1989, the Dark Avenger virus spread rapidly. The first polymorphic virus appeared in 1990. In 1995, they created a type of Macro Language virus called WinWord Concept.

As a result, we must protect computer users from spyware. We should also be careful about other malware. We need to know the potential risks in the digital environment. However, we must be sure of the software and download sources. In this way, we can reduce the risk of getting harmful things such as viruses.

Additionally, we should also try reputable anti-spyware apps. We should also make our antivirus programs efficient by constantly updating them. This provides adequate protection against viruses. Ultimately, with these measures, we can have a safer PC experience.

How Do Viruses Replicate or Spread?

The computer virus takes effect when it passes from one PC to another, thanks to executable codes. For example, if a virus becomes active on your device, it replicates by replicating itself. As a result, it quickly infects your floppy disks, hard drive, or network.

We see this type of infection on personal computers rather than large systems. Because we install our programs on disks and since we have a single network, we spread them across our network.

So, if we do something that will trigger viruses, they become active. Additionally, it multiplies and damages all our devices. Therefore, if a PC connects to an infected network, it does not become infected immediately. We activate it only when we access shared folders over a network.

Generally, we do not run potentially malicious code. Sometimes, viruses can trick our system or us. I’m specifically talking about those who work by complying with legal apps.

This adaptation occurs when we open or change the program. Thus, the virus becomes operational.

Additionally, the computer virus can settle in the boot sector of our host device. Thus, it runs automatically as soon as we turn on our PC. In networks, they try to hide within the software. Then, they wait for users to connect to the system.

How Are Viruses Infected?

The computer virus quickly settles in various places. Let me give you an example: main memory, macro documents, boot area, files, and websites.

  • Main Memory (RAM)

The virus threat automatically settles in the main memory, that is, RAM. Then, it waits to infect programs with EXE or COM extensions.

  • Document with Macro

A macro is a small program. It works primarily with tools such as Word, Excel, and PowerPoint. If we execute a macro in an office document, the virus will also run.

  • Booting

Hard disks and floppy disks have a boot sector. We may see viruses in this sector. For this reason, when we turn on our device, the virus runs immediately.

  • File

In particular, e-mail attachments are one of the effective ways to spread viruses. Attackers send malicious code through files with suspicious names and extensions.

  • Web Sites

Websites can also spread viruses. In particular, interactive pages, Java Applets, and ActiveX controls are examples of these.

What are the Types of Viruses?

We generally divide types of computer viruses into six categories. These parasites are first boot sector, multi-party, peer, connection, and data file.

1) Parasites

The parasitic type of virus infects executable files. They do not change the content of the main program. However, they stick in a way that executes the code. These viruses act directly or have built-in functions.

Direct-acting threats infect multiple programs. A resident threat is in memory, but if it runs, it infects specific apps.

2) Initial Boot Sector

These viruses settle in the first partition of our system disk. It then stores information about the contents of the disk. It also displaces programs that start the computer. As a result, it usually spreads when we use floppy disks.

3) Multi-Party

The multi-party computer virus has characteristics of parasitic and boot viruses. It infects both files and boot sectors.

4) Companion

Accompanying viruses do not modify files. However, it creates new programs with the same name as legitimate apps. That is, it works by tricking the operating system.

5) Link

The link virus type changes the way the operating system finds programs. It first runs the infected file and then the program you want. It triggers malware by infecting all executable apps in a directory.

6) Datafile

They often write data file viruses in macro languages. They automatically run when we run the legitimate program. It is machine and operating system-independent. Additionally, these threats infect software that contains powerful macro languages ​​that can open data files.

As a result, computer viruses are very diverse. Each causes harm in different ways. Therefore, it is vital to understand how viruses work.

Cleaning Analysis Algorithms

Heuristics are the ability of a protection solution to recognize malware without a signature. This allows the software to detect potentially malicious behavior. Our antivirus engine issues an alert when it detects suspicious behavior. Also, in this case, it indicates that the sample is potentially dangerous.

However, the antivirus cannot be entirely sure of an infected file. Because of that, it marked the file suspiciously with behavioral symptoms. This is not a 100% certainty. The system makes positive innovations in real-time or immediately. Behavior analysis constitutes a whole branch of science.

Intuitive mathematics is complex because it attempts to model behavior. Much of the time, the results of this approach remain inexplicable. We also know these techniques as mathematical discovery algorithms.

Algorithm logic is the mathematical modeling of behavior. It enables decision-making through discovery, observation & analysis. Multivariate analysis shows the dependence of an event on multiple factors.

Consequently, heuristics is a mathematical problem of multivariate exploration.

Signature Algorithm of Viruses

Many malicious codes are constantly changing. We can actually define these changes as a threat family. Additionally, antivirus software detects code similarities. In this way, it recognizes all viruses in the same family. Detection is possible with a single signature or global vaccine. We do not need to update the antivirus when a new version is released.

1) Code Recognition Algorithm

A program contains coding instructions during compilation. These instructions perform specific actions. Some antiviruses recognize these instructions closely. They use heuristic techniques to identify malicious codes in this way.

2) Assembly Language Algorithm

This algorithm method obtains source codes by examining executable files. Antiviruses analyze suspicious codes. It recognizes new codes without requiring updates. Also, it knows typical programming techniques.

3) File Hiding Algorithm

In this virus algorithm, the threat software hides its codes. That is, it uses file wrappers and packages like UPX, which are common. Antiviruses examine the actual code, not the package, by analyzing packaging methods.

4) Evaluation Algorithm

Intuitive virus scanning is challenging to evaluate. The antivirus momentarily stops updates and then collects new malicious codes. It analyzes performance by testing whether it can recognize these codes.

5) The Best & Most Appropriate Heuristic Algorithm

Heuristic algorithms do not provide precision. However, it gets as close to reality as possible. The best algorithm is the one that is close to actual behavior. Optimization factors play an essential role, but they aim to achieve minimum resource usage. It operates according to variable scenarios by reducing false positives.

These features make the antivirus suitable. The ability to approach reality is essential. The software takes into account multivariate threat factors. Moreover, the algorithm that recognizes all suspicious samples is not sufficient. The optimal algorithm gives more accurate results.

Minimizing the Possibility of Infecting a Computer Virus

Users should make backups to protect their computers. It is essential to create copies of the original software and data files.

Additionally, they should install the operating system on a protected disk. In particular, they should write-protect a floppy disk or CD/DVD device. In this way, they can render malicious files unwritable.

Briefly, download all the software you will use on your PC from reliable sources. Test new programs on a quarantined computer or virtual machine.

Also, write-protect floppy disks or others. By taking these precautions, you reduce the risk of infection. Additionally, you can prevent data loss by making regular backups, which is very important.

Virus Threat Detection

We can use various antivirus programs to detect the presence of a virus. Additionally, antiviruses recognize computer viruses’ codes. They can look for these features in computer files. As new viruses emerge, we must update our scanning tools to remain effective.

Some software looks for typical features of viral programs. These features tend to be less reliable. A single program can detect all viruses. It uses mathematical calculations for this. It also compares the states of executable apps.

If the checksum does not change, the system is not infected. However, checksum apps detect infection after it has occurred. Additionally, integrity programs detect potentially harmful activities. For example, they are overwriting computer files. Or like formatting the hard drive.

Integrity shells create layers through which the order of program execution must pass. They do automatic checksums in them. Also, when they detect harmful things, they do not allow it to work. As a result, these methods are effective in detecting & preventing types of computer viruses.

Recovery Stages

When we detect a viral infection, we must immediately isolate our devices on the network. Additionally, stopping file sharing is an extra method. We should not only take precautions for the disks we protect against writing.

We must delete the virus to get rid of the viral infection from our system. Some antivirus programs help us remove threats. However, sometimes the results are not satisfactory.

For effective recovery, it is necessary to disconnect the computer. We should also try to recover our data by booting from a write-protected disk. If we have affected files, we must delete them. In this case, we must replace our healthy files with backup copies again.

We need to delete any threats that may be present in the first boot sector. These methods provide more reliable results in the virus removal process.

Dissemination Strategies

Developers use a variety of strategies to evade antivirus programs. They also want to spread their projects more effectively.

Polymorphic viruses evade detection by changing their copies. This makes determining monitoring programs difficult. Stealth viruses simulate system consequences & disguise themselves. So, they’re hiding somewhere in our current operating system.

Fast infectious computer virus infects running & opened programs. This means that antiviral scanning software can infect entire software.

Slow viruses, on the other hand, only infect files when we modify them. This ensures that checksum programs see the changes intact. Some strategies infect one in ten running software.

This, unfortunately, makes detecting viruses difficult. As a result, this strategy is one of the most tactical steps we need to take.

Unauthorized Access

The biggest problem that computer security techniques must solve is unauthorized access to data.

  • In a secure system, we must ensure that the user logs in with a password before taking any action.
  • We must allow authorized users to access their devices by creating access codes. This is an effective method because it has hidden character strings.
  • We should not set access codes with a high probability of guessing.
  • In order to make it difficult for fraudsters, we must limit attempts to enter passwords on our PCs.

Frequently Asked Questions (FAQ) About the Virus

  1. How does a virus appear on a computer?
Computer viruses appear in different ways. However, of course, we cannot see them with the naked eye. Simply put, if your system crashes frequently, you have a virus at work.
So, if your PC has slowed down too much and you are getting an unexpected error message, run a scan. It is possible to see some viruses. If you’re receiving particularly annoying notifications, your PC is activated. You may also see some sites as your desktop background or homepage in browsers like Chrome.
  1. How do computers get viruses?
Computers are easily infected when we download infected files or software from the Internet. Even if the message sent to our e-mail address contains a threat, it is infected. We are also affected if we visit websites that automatically install malware. The most common one is to be sure to be careful with USB drives!
  1. What viruses are on the computer?
Since the field of PC viruses is very wide, we divide them into different categories. First, it is a Trojan horse. They gain unauthorized access to our systems through this seemingly innocent software. The second is worms. These spread by copying themselves into networks. The third is ransomware. In this type of virus, they encrypt our files and claim to send them back in exchange for money.


To summarize everything, I would like to briefly explain what a computer virus is. In summary, viruses easily infect our files & create unwanted threats on our PCs. For example, we may lose a project on which we spent a long time and effort due to a possible threat.

However, as technology advances, malicious people also make updates for viruses. They try many different methods and come up with new inventions.

As individuals or employees, we have to take precautions to protect our personal information. For example, we can use a potent antivirus tool that is popular in the market. As an extra, we must constantly back up the work or things we do.

As a result, we must ensure protection from cybersecurity threats. Whether you are a Windows, Linux, or macOS user, continually update your systems.

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