Home » Network Security Tutorial

Malware Types: Viruses, Worms, Trojans, and Ransomware

By IncludeHelp Last updated : July 27, 2024

What is Malware?

The term 'malware' refers to malicious software. Malicious means a desire to cause harm to someone by any means. Hence malware is defined as any software intentionally designed to cause damage to a computer, server, client, or computer network. In this tutorial, we will deal with the four most common types of malwares in detail.

Types of Malwares

There are various types of malwares employed which can destroy your system:

1. Viruses
2. Spam
3. Worm
4. Trojans
5. Ransomware
6. Spyware

The list above highlights some of the most common types of malwares. According to the latest reports, there are now over one billion malicious software, or malware, threats in circulation.

1. Viruses

Viruses are malicious programs that attach themselves to software or applications. When the infected file or application is used, the virus quickly spreads to other files and applications available on the system. Viruses can corrupt data, degrade system performance, and cause significant damage to software and hardware.

There are different types of viruses, such as:

• File Infector Virus
• Macro Virus
• Boot Sector Virus
• Polymorphic Virus
• Metamorphic Virus
• Resident Virus
• Direct Action Virus
• Multipartite Virus
• Web Scripting Virus
• Network Virus
• Overwrite Virus
• Spacefiller (Cavity) Virus

2. Spam

In your daily life, you have seen many spams over the internet, your mobile phones, etc. Spams are unsolicited, irrelevant, or inappropriate messages that are sent over the internet to a large number of users. Some of the examples of spam are: email spam, comment spam, SMS spam, phishing spam, etc.

3. Worms

Worms are malware that can spread by themselves from one computer to another. Unlike viruses, they don't need to attach to other programs. They exploit vulnerabilities in operating systems and applications to spread rapidly across networks. They can use up a lot of bandwidth, overload web servers, and cause significant damage.

Many types of worms spread through different methods. Email worms, like Melissa and Mydoom, spread via infected email attachments. Network worms, such as Sasser and WannaCry, exploit security flaws in networks to spread rapidly. File-sharing worms, like Mandragore and Tanked, disguise themselves as regular files on file-sharing networks. Instant messaging worms, like Bropia, spread through IM platforms by sending infected files to contacts. Internet worms, like Nimda and Morris Worm, exploit vulnerabilities in websites or web servers to spread.

4. Trojans

A Trojan Horse Virus is harmful software that pretends to be a normal program. It usually spreads through email attachments or free downloads. Once installed, it can steal data, spy on users, or give access to hackers.

There are different types of trojans, such as:

• Backdoor Trojan
• Banker Trojan
• Distributed Denial-of-Service (DDoS) Trojan
• Downloader Trojan
• Exploit Trojan
• Fake Antivirus Trojan
• Game-Thief Trojan
• Instant Messaging (IM) Trojan
• Infostealer Trojan
• Mailfinder Trojan
• Ransom Trojan
• Remote Access Trojan
• Rootkit Trojan
• Short Message Service (SMS) Trojan
• Spy Trojan
• SUNBURST Trojan

The Zeus Trojan, discovered in 2007, spread through fake emails and websites, tricking users into downloading it. Once installed, it silently steals sensitive information like online banking details, which leads to significant financial theft. Law enforcement eventually took action against Zeus, but its variants continue to pose a threat. This highlights the importance of being careful with email attachments and downloads.

5. Ransomware

Ransomware is a computer virus that gets into your computer and locks up your important files. Then, it asks you to pay money (a ransom) if you want to get your files back.

There are two types of ransomwares, namely:

• Encrypting Ransomware: It locks up your files and asks for money in exchange for the key to unlock them.
• Non-Encrypting Ransomware: It blocks access to your entire device and demands payment to unlock it.

In 2017, a big ransomware called WannaCry attacked computers worldwide. It locked up files and demanded money from users to unlock them. It spread quickly because it exploited a weakness in Windows computers. Many organizations, including hospitals and businesses, were affected by this attack.

6. Spyware

Spyware is also a type of malware, and it is used for gathering information about an individual or an organization without knowing them. Some of the types of spyware are: Adware, system monitors, tracking cookies, etc.