10 Common Types of Malware (Virus) You Should Know


Learn about the common types of malware and their differences, so you can understand how virus, trojan and other malware work.< /i>

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There are many types of malware that can affect your computer. And although many people use the term “virus” as a general term for a program that attacks a computer system.

Let’s define and explore the most common types of online threats today. You’ll learn how each one works, and the difference.

Malware Defined

Malware, short for “Malicious Software“, is a general term for malicious applications. This is a more appropriate term for bad software than “virus”. You can use “malware” to refer to the other types we’ll be talking about, such as viruses, Trojans, ransomware, and more.

This is why you’ll hear many apps, like Malwarebytes, as “anti-malware” solutions, not just “antiviruses”.

1. Virus

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Virus is a malicious program that replicates itself. It does this by inserting its code into another program to propagate itself.

Viruses usually enter a person’s system by running infected files from email attachments or flash drives. It’s also how much other malware gets into a person’s system, so that alone doesn’t define a virus. The main differentiating factor is that the virus attaches itself to other programs, and reproduces itself by modifying various software behind you.

Viruses have been around for decades; Viruses first appeared in the early 1980s. This attack used to be more common in the 1990s and early 2000s, but has recently become less popular as it supports other types of attacks.

2. Worm

Worms are similar to viruses; the difference is that the worm spreads by itself rather than attaching itself to a program and infecting that program and others. Often times, worms spread across networks, exploiting vulnerabilities to jump from machine to machine.

As they continue to propagate recursively, the worms infect machines at a faster rate. This minimally consumes network bandwidth, while more malicious worms can spread ransomware or other problems across a business network.

3. Trojan Horses

Trojan Horses, often called trojans, are malicious programs that trick you into thinking they are legitimate tools.

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The name comes from the story about the Trojan Horse, where the ancient Greeks left a wooden horse filled with their soldiers near the city of Troy. The Trojans took their horses to their city, thinking they had won the battle. However, at night, the Greek soldiers jumped out of the horses and let the rest of their troops enter through the city gates, entering the city of Troy.

A computer trojan works the same way. Trojans masquerade as genuine software, such as a form to fill out or a useful application. However, once on your system, the trojan sends a payload(virus file).

In other cases, the trojan might even delete your files, run a ransomware infection, or something else.

4. Adware

Adware is a type of malware that spawns ads to make money for its developers. While ad-supported software is common in mobile apps and even some desktop tools, adware goes a step further by flooding users with ads.

For example, adware might push additional ads to every web page you visit, or turn your browser’s search engine into a scammy engine designed to redirect you to sites that make more money for their owners. Some adware also shows popups on your desktop which are difficult to close.

There’s a fine line between legitimate ads as a way to monetize apps, and programs designed for spam popups that annoy you. Adware is often bundled onto your system alongside legitimate software via a pre-checked checkbox during the installation process.

5. Spyware

Spyware is another type of malware that can take several forms. This refers to a program that tracks your computer usage for some purpose and reports it back to the entity.

Most programs – and even operating systems like Windows 10 – collect data about your usage and report it back to the developer. They use this to enhance their tools with real-world data. Precise spyware is distinguished by the fact that it collects this data without notifying the user.

While spyware often collects your data for advertising purposes, malicious spyware can also collect sensitive information such as login credentials. Extreme spyware includes keylogger, which is a program that records every keystroke you make on your machine.

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6. Ransomware

During the late 2010s and beyond, ransomware skyrocketed in popularity. This is a destructive type of malware that encrypts the contents of your computer, locking you out of your own files. Ransomware demands that you pay the creator, usually through an untraceable method like Bitcoin, to obtain the encryption key and unlock your files.

The best way to stay safe from ransomware is to make a plan. Keeping regular backups of your files will allow you to restore them in case you are hit by a ransomware attack.

7. Scareware

Scareware is somewhat similar to ransomware, except that it only pretends to be dangerous.

Typically, scareware manifests through rogue online advertisements that take over your browser. It shows a fake virus warning message , claims that Microsoft, Google, or another company detected a problem with your computer, and directs you to call a phone number or download “antivirus software” to fix it.

If you dial the phone number, you’ll be talking to a scammer who wants you to pay for a useless cleaning process. Fake antivirus software is the same; it asks you to pay for worthless apps just so the criminals can make money.

Fortunately, you can usually close the scareware popup and ignore the message. They are designed to exploit people through fear and not actually harm your computer. The real threat is wasting your money.

8. Rootkits

A rootkit (a term combining the “root” admin account on Unix systems and the “kit” they use) is a type of malware that gains access to certain parts of a computer and then disguises itself or hides itself.

Typically, rootkits are installed when the attacker has admin (or root) access to the machine. Once the rootkit is installed, it has the privilege to do whatever its owner wants on the system. Rootkits abuse this to hide their intrusion – for example, rootkits may hide their existence from installed antivirus applications.

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Obviously, malware that has complete control over your system is quite dangerous. Often times, you have to completely reinstall the OS to remove the rootkit.

9. Botnets

Botnets are more the result of a malware attack than a specific type of malware, but are still relevant for discussion here.

Botnet (which is a combination of “robot” and “network”) is a term that refers to a group of computers or other network devices that are slaves of an entity. The controller then uses the machine to perform tasks, such as DDoS attacks, send spam, or click ads in the background to make money for the owner.

Computers can become part of a botnet by running trojans or other infected files. Most of the time, your computer will continue to function normally, so you may not even know you’re part of a botnet.

10. Exploitation and Vulnerability

Although not in the form of malware, Exploitation and Vulnerability is an important term in online security. Because no programmer or software is perfect, every program, OS, and website has some kind of vulnerability. Malicious actors work to find these flaws so they can exploit them to run malware or the like.

For example, someone discovered a bug that allows you to create a new admin account without a password in Windows by following certain steps. Someone could write malware to run these steps on someone’s PC, gain admin access, and then wreak havoc.

The best way to stay safe from this threat is to keep your OS and all software up to date. Developers fix these issues as they discover them, so staying on the latest version keeps you safe from old and known exploits.

Understanding the Most Common Malware Threats

Now you understand the most common types of malicious “Virus” and what distinguishes them. There is often overlap – for example, trojans can be used to run ransomware. But most types of malware have distinct features that set them apart.