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Types of Computer Viruses

Virus detected on a computer

“Creeper,” the first computer virus, hit servers over 50 years ago. However, Creeper wasn’t used for nefarious purposes. It was a test to see if programmed code could self-replicate, and it is known as the first “worm” virus. 

In the decades since, and especially since the dawn of the Internet, computer viruses have been used maliciously by cyber criminals all over the world.

Modern computer viruses come in many iterations, and inoculation against all viruses is virtually impossible. Yet, in an increasingly online world, there are ways to protect yourself against the damaging effects of these viruses. It’s important to know the most prevalent types of computer viruses and how to protect yourself from them.

What you need to know about computer viruses

Computer viruses can do a lot of damage to your operating system (OS). They can expose and corrupt your personal data and can go undetected before their damage is done. It’s important to take steps to protect yourself against these viruses and learn how to detect their dark ways before they attack.

The average cost to repair a data breach caused by a computer virus is $3.86 million. If you don’t have personal and professional antivirus software protection in place, you may find yourself in a financial mess.

Malware code snippet on a computer monitor, highlighting the complexity of computer viruses

What is a computer virus?

A computer virus is code written with the sole purpose of duplicating itself and infiltrating computer systems. Most hackers focus on attacking various businesses. They may infect an entire network of servers to lock systems and launch ransomware

However, these cybercriminals may infiltrate personal servers by attaching their code to suspect websites or email links, too. 

In 1974, a mere three years after Creeper was introduced, the Rabbit virus, also known as a fork bomb, was one of the first used to clog and corrupt a computer’s system. The Rabbit quickly replicated itself and slowed down performance before crashing entire operating systems. It is the first known “bad actor” computer virus and cyberattack.

Most common computer viruses and real world examples

Computer viruses can appear through various methods and use different types of malicious code. There’s an army of computer viruses waiting to take up arms and cause damage. But certain types of computer viruses are more prevalent.

Let’s take a look at some of the most common viruses, how they work, and real life examples of the havoc they can wreak.

Boot sector viruses

The boot sector virus doesn’t incur the damage it once did, as it spreads its infection through floppy disks. This virus lays its groundwork in the boot sector of a disk. Then it infects a computer via the disk during system boosts. Thus, from 1995 forward, the boot sector virus mostly lost its ability to carry out its villainous ways.

One of the most famous examples of the boot sector came via the Michaelangelo virus in 1991. The Michaelangelo was designed to rewrite or overwrite vital data for a computer’s operating system, thereby rendering it useless.

Browser hijacker

The browser hijacker virus is a form of malware that forces your browser to open websites that you didn’t search for or want to open. Typically, these sites are run by hackers who then infiltrate your computer to steal your confidential information.

For example, the Babylon Toolbar is a modern adware browser hijacker that overrides your browser settings and changes your homepage to This insidious malware is easily detected as you’ll notice Babylon ads cropping up every time you click open your homepage.

Cyborg ransomware

Cyborg ransomware first reared its ugly, infectious head in 1989 via the famous AIDS (Aids Info Disk) Trojan Horse  virus. It hits operating systems and remains undetected until it has thoroughly infected your files. It’s one of the most agressive forms of ransomware.

Cyborg is a malicious software program that renames and reroutes files during the encryption process. For example, any file stored on your computer with a safe .pdf or .jpeg assignment becomes a .pdf.petra. Once the process is complete, cyborg takes over your computer and changes your wallpaper to reflect its control of your OS. 

Only the original virus program can restore your computer to full health. After the cyborg takeover is complete, you’ll receive payment demands from the cybercriminals responsible for the attack.

Direct action viruses

This malware exposes itself via computer issues such as random pop-ups, corrupted or missing files, and browser redirects. A direct action virus attaches itself to .exe files and .com files to infect your operating system. 

The direct action virus can go virtually undetected as it becomes ingrained in your computer’s memory. This cyberattack will steal your personal data and corrupt or delete your files.

In 1987, the Vienna virus was introduced as a form of direct action malware. Every time a user opened a corrupted file, it started searching for uninfected files to corrupt. It then worked in conjunction with the AIDS computer virus. 

Polymorphic viruses

The polymorphic virus sounds like something straight out of a science fiction film. Its abilities to shapeshift certainly adhere to the genre. However, there’s nothing fictional about this type of computer virus or how it can infect your computer.

Polymorphic viruses are programmed to mutate through different forms of decryption. These malicious bugs may get through standard antivirus software protection. Then they can launch a multi-layered attack which makes the malware harder to erase.

The Storm Worm, one of the most well-known examples of a polymorphic virus, deceived users into downloading trojan malware through phishing schemes. This worm attacked private servers throughout the U.S. and Europe in the early 2000s.

Resident viruses

Resident viruses may not display the same type of malevolence as Resident Evil video game zombies, but they can cause major headaches and stress. As the name implies, a resident virus takes up residence on your hard drive. It can infect any program your computer runs — including antivirus software.

By attaching itself to an antivirus program, the resident virus then infects all scanned files. Like many of its viral counterparts, the resident virus is great at hiding and its depths have no bounds. This malware can impact every file on your server.

Resident viruses also go by the fear-inspiring nickname “Terminate and Stay” and are tough to destroy.

Web scripting viruses    

Web scripting viruses are focused on large scale attacks against major websites. The web scripting virus infiltrates the security of a web browser by exposing its vulnerabilities and cybersecurity flaws. It then allows a cybercriminal to hack in and inject malicious code. 

Comment sections, email providers, and social networks are also especially vulnerable to these attacks. For example, a DDoS (Distributed Denial of Service) attack utilizes web scripting.

Unlike the resident virus, the web scripting virus blatantly attacks. Typically, the user is quickly made aware of its negative effects. For instance, if your smart device shuts down or if you discover your Facebook page has been hacked, you may have suffered a web scripting attack.

Computer virus protection with a lock symbol, symbolizing robust cybersecurity measures safeguarding against malware and threats

How to protect yourself against computer viruses

Unfortunately, you can’t prevent every cyberattack or prepare for the numerous types of computer viruses that can worm into your operating system. However, there are measures that you can take that can greatly reduce your risk and chances of stolen personal information.

Some of the ways to protect yourself against computer viruses include:

Antivirus software:

Although many antivirus packages require a yearly payment, there are some free antivirus software programs that might meet your needs. Some smart devices even come equipped with pre-installed antivirus software. 

Ensure all security protections are up-to-date on your device:

Install any updates to your security software. Using an out-of-date program may leave your device vulnerable to all types of computer viruses.

Regularly scan your system:

Most antivirus software packages allow you to set automatic scans, but it’s vital that you regularly run a system scan. If there are any unknown or suspicious files, your antivirus program will automatically alert you and allow you to remove these files or protect your device from their installation.

Never use unsecured WiFi networks to send or receive personal data:

If you access a public, unsecured WiFi network, avoid using this for online activity such as checking your email or bank statements, making payments, or sending private information.

Ensure the websites you’re visiting are secure:

Most web browsers will alert you to the security of a site, but it’s easy to forget to check a site’s status. If you’ve already clicked on a suspect website, look for the lock icon in the address bar (this appears before the https segment of a site’s address).

If you’re using Google, you can also right-click on a search result’s heading to ensure a website has been indexed. When the results appear, Google will also alert you to the security of the site you want to visit.

If you’d like to learn more about tips and insights into cybersecurity, check out the   What Is My IP Address blog and access the free cybersecurity tools on our homepage.

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