As long as computers have been stable enough, people have found ways to cause problems. One of the most effective ways to create mischief on a computer is through malware, such as a computer worm or virus. Let’s discuss about computer viruses in detail, explaining how they come into existence and how they can affect our systems.
Table of Contents
What is a Computer Virus?
We hear about it in the news almost weekly these days, but what is a computer virus?
A virus is also software, a piece of code that can self-replicate. It can spread quickly from one computer to another and cause abnormal performance. A virus is a sort of malware that attaches itself to the host file during execution and spreads throughout the system.
It replicates itself by creating files and attaching itself to genuine software, allowing the user to run the virus. It can only spread with human interaction. When the replication succeeds, the affected areas are said to be infected with a computer virus. It can steal passwords and data, log keystrokes, corrupt files, spam your contacts, or even take over your machine.
History and Spread of Computer Viruses
Viruses were created for nefarious objectives. People generate viruses for various purposes, ranging from harmless fun to malicious destruction.
The concept of an autonomously self-replicating entity dates back to the 1940s. Creeper was constructed and deployed onto the ARPANET in 1971. Creeper would bounce between computers, leaving only a message written on the teletype terminal, “I’m the creeper. Catch me if you can.” Later versions of the program would drop a duplicate of itself on the visiting machine, making Creeper the first application to spread copies of itself autonomously on other systems. Thus, Creeper was the first computer virus created.
Another virus known as Elk Cloner would add itself to the system’s boot sector and be used to boot Apple devices, which would then add the cloner to every subsequent disc placed into the system by writing into the boot sector.
There are six common ways through which viruses spread.
1. Opening attachments or links from unknown and fake emails
This is one of the most popular methods to infect with a virus or ransomware. Emails are spoofed to appear authentic; they contain an attachment or link that will infect your machine when clicked. These counterfeit emails are so well-crafted that even a seasoned professional can be caught off guard if not careful.
2. Downloading software from malicious sites
When your computer gets infected with a virus, you might think the website is not trusted. It is a common misconception that viruses only come from inappropriate or problematic websites. However, viruses are dangerous and are everywhere on the Internet.
3. Online ads
Malicious internet adverts, often known as malvertising, are yet another way for your computer to be infected with a virus without your knowledge or traceability. Criminals frequently install clean advertising on trusted websites and leave them there for some time to establish credibility. After some time has passed, they insert a harmful code inside the ad that, when clicked on, infects your computer.
People are generally more relaxed about clicking on links published on social media sites. Malicious links on social media sites may contain viruses that may be harmful to your computer or any other device.
5. Unpatched software
Another way you put your computer at risk of a virus infection is through unpatched software. Security holes, unknown to the software makers or anti-virus vendors, are also known as zero-day vulnerabilities.
6. Pirated software
An illegal copy of software is called pirated software. Some companies intentionally add a virus to pirated software.
Types of Computer Viruses
The different types of computer viruses are:
Resident Virus
A resident virus installs itself in your RAM and interferes with system operations. It is so cunning that it can attach itself to anti-virus software files.
Multipartite Virus
This virus infects the entire system and is spread by performing unauthorized actions on your operating system, folders, and programs.
Direct Action Virus
This virus targets a specific file type, most commonly executable files (.exe), by replicating and infecting files. Due to its targeted nature, this virus type is one of the easier ones to detect and remove.
Browser Hijacker
This type of virus is easily detected. It infects your browser and redirects you to malicious websites.
Overwrite Virus
As the name implies, overwrite virus overwrites file content to infect entire folders, files, and programs.
Web Scripting Virus
This sneaky computer virus disguises itself in coding links, ads, images, videos, and site code. It can infect systems when users download malicious files or visit malicious websites.
File Infector Virus
By targeting executable files (.exe), the file infector virus slows down programs and damages system files when a user runs them.
Network Virus
Network viruses travel through network connections and replicate themselves through shared resources.
Logic Bomb
The logic bomb virus is triggered by a specific condition, after a certain number of transactions, or on a specific date and time. This virus is also called a time bomb.
Trojan Horse Virus
This virus performs illegal and damaging instructions in the middle of a program, such as a computer game. This virus includes concealed instructions to wipe data, such as formatting the C drive, which could result in massive data loss.
Now, as we already know about the various types of viruses, so let’s see what impact they can have on our system.
Effects of Computer Viruses
The following are the effects of a computer virus:
1. Processing and internet speeds are slower
A slower computer does not always indicate the presence of a virus, but if there is a significant shift in speed, then there is a chance that your computer is affected by a virus,, and it is better to check the system for it.
2. Unexpected computer behavior
A virus can do all kinds of strange things to your computer. If your computer stops responding to clicks, decides to open files on its own, scrolls, or acts as if a key has been pressed when it has not, then the system is probably affected by a virus.
3. Sudden freezes and crashes
Because viruses damage the hard drive, they can cause your computer to experience a catastrophic failure.
4. Error messages
Your computer knows that something is wrong before you do. One of the most noticeable effects of a computer virus is the sudden appearance of pop-up messages warning you about missing system or application files.
Keep track of the size of your hard drive. A virus can install files of itself or unwanted files on your computer. Viruses can also delete files unexpectedly.
6. Hardware and accessory problem
If your computer’s display suddenly has problems, such as mixing pixels or colour problems, it can be a sign that a virus has infected your system.
Preventing and Removing Computer Viruses
We rely on computers for a variety of tasks. We place our trust in them to keep our information safe, including our files and personal data, which is why it is critical to protect your computer and do everything you can to keep it functioning.
Here are some tips to protect to prevent viruses:
- Anti-virus software, such as Kaspersky, Norton, or Windows Defender, should be used. Anti-virus software prevents viruses from being installed and also allows you to search your computer for viruses and remove them if any are discovered. Remember that no anti-virus program is perfect, so to keep secure, avoid suspicious-looking adverts or downloads and frequently run anti-virus program updates.
- Do not click on any pop-up adverts.
- Make sure that your operating system is up to date as well.
- When accessing unsolicited emails, inspect them thoroughly.
- Carefully analyze the documents acquired from file-sharing websites.
Remove Virus From Computer
If your PC is infected with a virus, you can get rid of it by following the below-mentioned instructions:
- Start in Compatibility Mode. The procedure will differ depending on your Windows version or other operating system.
- Remove any registry entries. Use the repair disk program to erase the temp. folder while in standby mode.
- Get legitimate and on-demand antivirus software.
- Start the on-demand scanner first, then the legitimate scanner. If neither scanner eliminates the virus, it may be necessary to remove it explicitly. This can only be done by a professional who is familiar with the Windows Registry and can inspect and delete system and program files.
- Reinstall any files or programs that the malware has corrupted.
Top 10 Computer Virus in 2025
The top 10 computer viruses in 2025 are :
1. Conficker
Conficker was released into the wilds of Windows to steal administrator passwords and create a botnet. It infected 15 million corporate, government, and home PCs, making it the single largest computer virus infection in the last five years. It caused nine billion dollars in economic damage.
2. SQL Slammer
SQL Slammer spreads so rapidly that 75,000 infections occurred within a span of 10 minutes. It is a denial-of-service attack that targets users’ favourite websites, causing them to crash.
3. Stuxnet
Computer viruses are usually more of a nuisance or costly problem than highly engineered weapons capable of causing real-world damage. Stuxnet, which was used to take down rands, may have been the first weapon entirely made out of code. It is considered the most dangerous computer virus.
4. Boot Sector Virus
The boot sector is the first sector of the hard disk where the boot program is stored. The boot program loads the operating system into memory. The virus attaches itself to executable files, such as .exe, .com, and .dll; when users use these files, the virus is activated. It affects the booting process of an infected computer system.
5. Chernobyl Virus
When an infected file is executed, the Chornobyl virus deletes all Microsoft Office files and computer data. It also deletes the partition information from the hard disk, causing a major data loss.
6. Redlof
Redlof is a polymorphic virus built in a basic visual script. It embeds itself without any attachments in every email sent from the infected system and attacks a file named folder.sst.
7. Macro Virus
A macro virus is a computer virus that is inserted as a macro in a document. A macro is a sequence of commands that can be stored and recalled with a single command.
8. Code Red
Code Red wreaked havoc and annoyed users all over the internet. It also launched a denial-of-service attack and targeted the White House website.
9. Storm Virus
Storm virus was a backdoor Trojan Horse that was released on the internet back in January 2007 to infect computers running Microsoft Windows operating systems.
10. Sasser and Netsky
Sasser is part of the Netsky family of viruses. These viruses attack vulnerable PCs through an open port, which your firewall protects against. Their release in 2004 caused widespread problems.
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Conclusion
In this era of digitalization, cyberattacks are becoming more common every day. So, it is our responsibility to be safe from malicious viruses and other sources of attacks. As technology advances, we also need to take the necessary measures to counter these threats by updating our resources periodically.
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