12 Common Types of Malware: Threats and Prevention

Ever clicked on a suspicious link or downloaded an email attachment without thinking twice? If so, you’ve already faced the risk of falling victim to malware. Cybercriminals use different types of malware every day to steal data, disrupt systems, and hold devices hostage.

Understanding the common types of malware is the first step in protecting yourself and your organization. In this guide, we’ll break down 12 of the most dangerous malware threats, explain how they work, and share practical tips to keep your devices secure.

What Is Malware?

Malware (short for malicious software) is any program or file created with the intent to damage, disrupt, or gain unauthorized access to a computer system. Cybercriminals use malware to steal sensitive information, monitor user activity, or take control of devices for their benefit. Understanding the common risks associated with malware infections is essential, as even a single click on a malicious link can lead to severe data breaches or performance issues.

A common misconception is that the terms virus and malware mean the same thing. In reality, a virus is just one type of malware. While malware is the broader category that includes many different threats, like ransomware, spyware, computer worms, and trojans, a virus specifically refers to malicious code that spreads by attaching itself to other files or programs.

Simplify Malware Security with PowerDMARC!

12 Common Types of Malware You Need to Know

Every year, businesses face escalating cyber threats, with attacker tools evolving at an astonishing pace. In 2023, over 6 billion malware attacks were detected globally, most in the Asia-Pacific region.

These facts are even more concerning given the rise of remote startups. Operating on smaller budgets and relying heavily on technology, they are more susceptible to cyber threats and may be less equipped to deal with the cost of recovery.

Malware comes in a variety of forms, including:

1. Computer Viruses

A computer virus is one of the oldest forms of malware. It attaches itself to legitimate files or applications and requires a host file to spread. When the infected file is opened, the virus executes and can corrupt data, slow down systems, or spread to other files and devices. Because viruses need user interaction (like opening an attachment), they often spread through email, file-sharing, or USB drives.

2. Worm

A worm is a program replicating itself to spread from one computer to another. Unlike a virus, however, it does not attach itself to other programs or files on your computer. Instead, it travels through the Internet searching for vulnerable computers, installing itself on those systems, and replicating. 

Worms usually cause more damage than viruses because they multiply quickly and easily.

3. Ransomware

Ransomware is one of the most financially devastating types of malware. It encrypts a victim’s files and demands payment, often in cryptocurrency, for the decryption key. Entire organizations can be paralyzed, with critical data and systems locked. 

Recent attacks on hospitals, city governments, and pipelines demonstrate the significant financial, operational, and reputational impacts of ransomware, making recovery from such attacks particularly challenging.

4. Spyware

Spyware is malware that secretly installs itself on a device and monitors user activity. It often hides in free software downloads, phishing links, or malicious ads. 

Spyware can collect:

• Login credentials (usernames and passwords)
• Credit card and banking details
• Browsing history and personal data

The stolen information is sold or used for identity theft and financial fraud.

5. Trojan Horse

A Trojan horse is malicious software that masquerades as useful or legitimate. When you open an email attachment containing a Trojan horse or click on a Web link leading to one, you allow the Trojan horse access to your computer — sometimes without even realizing it until it’s too late!

The most common types of Trojan horses are:

• Keyloggers, which record everything you type on your keyboard.
• Bots (short for robots), which hackers use in distributed denial-of-service (DDoS) attacks.
• Password stealers.
• Remote access tools (RATs).

6. Keyloggers

Keyloggers track and record every keystroke a user makes, often without detection. This allows attackers to capture sensitive data like:

• Passwords
• Credit card numbers
• Private messages

Keyloggers can be installed via Trojans, phishing links, or physical devices plugged into a computer.

7. Cryptojacking Malware

Cryptojacking malware hijacks a victim’s device to mine cryptocurrency without permission. It consumes processing power, electricity, and hardware lifespan, often slowing down the device dramatically. 

Delivery methods include:

• Visiting an infected website
• Downloading malicious files
• Clicking phishing email links

While less destructive than ransomware, cryptojacking drains resources and damages equipment over time.

8. Rootkit

A rootkit is designed to gain administrator-level control over a system while staying hidden. Once installed, attackers can manipulate files, disable security tools, or steal data, all without the user noticing. Rootkits are notoriously hard to detect and remove, often requiring a full system reinstall to eliminate.

9. Fileless Malware

Fileless malware doesn’t rely on traditional files to infect a system. Instead, it operates in a computer’s RAM and uses legitimate built-in tools (like PowerShell or WMI) to execute malicious commands. Because it leaves little to no trace on disk, it can bypass most antivirus solutions. Fileless attacks are increasingly common in targeted campaigns.

10. Adware

Adware delivers unwanted advertisements on a user’s device. While some adware is relatively harmless and just annoying, malicious adware can also track browsing activity and collect personal data for targeted scams. For example, it may harvest user preferences, search history, or even location data to sell to third parties.

11. Botnets

A botnet is a network of compromised devices (called “bots” or “zombies”) under the control of a hacker (the “bot-herder”). Once assembled, botnets can:

• Launch massive DDoS attacks to overwhelm websites or services
• Send millions of spam or phishing emails
• Perform credential stuffing using stolen logins

Botnets turn ordinary devices into weapons without their owners even knowing.

12. Wiper Malware

Wiper malware is designed for pure destruction. Unlike ransomware, which demands payment, wipers erase all data on an infected system with no chance of recovery. Often used in cyberwarfare or sabotage campaigns, wipers target governments, enterprises, and critical infrastructure to cause maximum disruption. The NotPetya attack (2017) is a well-known example that crippled global companies.

How To Prevent Different Types of Malware?

Malware continues to evolve, but most attacks exploit the same weaknesses, such as outdated software, careless clicks, and weak security practices. While no single solution can guarantee complete protection, combining good cyber hygiene with proactive defense measures greatly reduces your risk.

Here are practical steps you can take:

• Keep your software up-to-date: Regularly update your operating system, applications, and security tools to patch known vulnerabilities.
• Use reputable security solutions: Install antivirus, anti-malware, and firewalls to detect and block threats before they spread.
• Beware of suspicious emails and links: Avoid clicking on unknown attachments or links in phishing emails, which is the most common malware delivery method.
• Download from trusted sources: Only install software from official websites or app stores to avoid Trojans and spyware hidden in free downloads.
• Use strong, unique passwords: Prevent malware-assisted credential theft by protecting accounts with strong and unique passwords (and ideally, multi-factor email authentication).
• Backup your data regularly: In case of ransomware or wiper attacks, backups ensure your data can be restored without paying criminals.
• Limit user privileges: Restrict administrative access so malware like rootkits can’t take full control of your system.
• Monitor system behavior: Watch for unusual activity such as slow performance, high CPU usage, or unexpected pop-ups since these may indicate an infection. You can use free tools to track CPU usage and CPU temperature, helping you spot sustained spikes or abnormal system activity that may signal malware.

Stay Vigilant, Stay Protected

Malware threats are constantly evolving, and it’s understandable to feel overwhelmed by the variety of attacks, from viruses and ransomware to rootkits and fileless malware. 

The good news is that you don’t have to face these risks alone. By adopting a proactive, multi-layered security strategy that combines clear processes and user awareness, you can protect your organization and its people.

See how PowerDMARC helps you implement DMARC to block threats before they reach the inbox.

Frequently Asked Questions

Is all malware considered a virus?

No. While a virus is a type of malware that attaches to files, malware also includes worms, ransomware, Trojans, spyware, and other malicious software.

What is the strongest malware in the world?

“Strongest” depends on impact and reach. Malware like Stuxnet, WannaCry, and NotPetya caused widespread disruption and financial damage, making them some of the most powerful in history.

What is the hardest type of malware to detect?

Fileless malware and rootkits are among the hardest to detect because they operate in memory or hide system-level activities, often bypassing traditional antivirus software.

• About
• Latest Posts

Ahona Rudra

Domain & Email Security Expert at PowerDMARC

Ahona is the Marketing Manager at PowerDMARC, with 5+ years of experience in writing about cybersecurity topics, specializing in domain and email security. Ahona holds a post-graduation degree in Journalism and Communications, solidifying her career in the security sector since 2019.

Latest posts by Ahona Rudra (see all)

• CSA Requires DMARC for Cyber Essentials Mark Certification - February 10, 2026
• Practical DMARC Deployment for MSPs and Enterprises: What Most Guides Miss - February 9, 2026
• PowerDMARC Now Integrates with Elastic SIEM - February 5, 2026