10 Most Common Types of Malware

In today’s rapidly evolving technological environment, the threat of malware looms larger than ever before. Here, we explore the most common malware categories and how to keep them out of your network.

Malware represents a major threat to business operations — and unfortunately, that threat is growing. In 2022 alone the number of malware attacks around the globe rose to 5.5 billion reported cases — 100,000,000 more cases than were reported in 2021. But malware isn’t only getting more common; it’s also becoming more advanced. Just like the biological viruses many of them are designed to mimic, new types of malware are evolving at an astounding rate.

Today’s malware employs highly sophisticated attacks that can wreak havoc on individuals, organizations, and even entire nations. As such, the digital world has become a battleground where businesses and individuals must arm themselves with robust security systems to defend against this ever-growing menace. And while having the right digital systems must certainly be a central factor in any organization’s security strategy, an aware and educated workforce will always be the first line of malware defense.

Simply put, the first step to protecting your vital data, systems, and networks is knowing what kind of threats you may encounter. Here, we review the 10 most common types of malware, and how you can help ensure that they don’t infect your business.

But first, let’s take a look at what malware actually is.

What Is Malware?

Malware (short for “malicious software”) refers to any software or code designed or employed with malicious intent to disrupt, damage, or gain unauthorized access to computer systems, networks, or personal devices. This term encompasses a wide range of entities of varying degrees of sophistication. Regularly used in conjunction with phishing attacks or other infiltration attempts, malware is often disguised as legitimate software or files — deceiving users into unknowingly installing or executing the malicious program within the targeted network.

Malware is a pervasive threat, one that poses a significant danger to individuals, businesses, and society as a whole. These malicious programs are designed to steal or compromise sensitive data and disrupt standard business operations. Sometimes the damages from a single malware infection can take months to repair, and that timeframe becomes even longer if the malware remains undetected in the network.

The financial impact of malware attacks on businesses is staggering. These costs include expenses related to data breaches, system repairs, legal and regulatory penalties, lost productivity, reputational damage, and the implementation of enhanced security measures to prevent future attacks. In 2023 the total annual global cost associated with cybercrime is expected to reach $8 trillion — that’s more than the gross domestic product of any single nation on earth, excluding only the United States and China.

But perhaps even more alarming is that the dangers of malware extend beyond financial implications. The theft of personal information can lead to identity theft, fraud, and other forms of cybercrime, impacting individuals and their trust in online systems. And on a larger scale, critical infrastructures such as healthcare systems and power grids are often targeted by malware attacks, putting lives directly at risk.

What Are the 10 Most Common Types of Malware?

Although new variations are constantly discovered and cataloged, the truth is that most malware attacks tend to fall into one of 10 distinct categories. Understanding these common types of malware is crucial in fortifying your defenses and staying one step ahead of potential threats.

The 10 types of malware that you are most likely to encounter include:


Ransomware is a type of malware that encrypts the victim’s files, rendering them inaccessible until a ransom is paid to the attacker. This malware often infiltrates systems through malicious email attachments, fake software downloads, or compromised websites. Once activated, ransomware employs strong encryption algorithms, making them unreadable without the decryption key held by the attacker. The victim is then presented with a ransom demand in exchange for the decryption key.

Identifying ransomware before it deploys can be challenging, as it often disguises itself as legitimate files or software. However, once it infects the system it quickly reveals itself through the inability to access files, the appearance of ransom notes on the screen or in encrypted file directories, and unusual file extensions added to encrypted files (such as .crypt or .locked).


Viruses are malicious programs that replicate themselves by infecting other files or systems. They can spread through infected email attachments, shared network resources, or even compromised websites. Once a virus infects a system, it can modify, corrupt, or delete files, disrupt system functionality, and replicate itself to infect other devices.

Identifying a virus infection may involve observing unusual system behavior, such as frequent crashes, slower performance, unexpected error messages, or unresponsive applications. Additionally, antivirus software can detect and quarantine known viruses.


Adware is designed to deliver unwanted advertisements to users. It often enters systems bundled with otherwise-legitimate software downloads or is intentionally spread to unsuspecting targets through deceptive advertising practices. Adware displays intrusive advertisements or redirects users to advertising websites, negatively impacting the user experience and system performance. In some cases, adware may collect sensitive user data to deliver targeted advertisements.

Signs of an adware infection include the persistent display of unwanted advertisements, unexpected browser redirects, changes to browser settings without user consent, and a sudden increase in the appearance of ads during online activities.

Fileless malware

Fileless malware operates out of the computer’s memory instead of from within the hard drive. Unlike traditional malware that relies on malicious files or executables, fileless malware exploits vulnerabilities in legitimate software to carry out its malicious activities. This type of malware often goes undetected by traditional antivirus solutions that primarily focus on file-based threats.

Because it takes such a different form when compared to most other types of malware, it can be difficult to identify a fileless malware infection when one occurs. That said, some indicators include unexpected system behaviors, abnormal network traffic, suspicious processes running in memory, or unusual CPU or memory usage.


Worms are self-replicating malware that spread across networks by exploiting security vulnerabilities. Once a worm infects a system, it scans the network for other vulnerable devices and uses various propagation methods — such as email, instant messaging, or network shares — to infect those systems. Worms can consume network resources, slow down systems, and facilitate the distribution of other malware.

Identifying a worm infection may involve observing a significant increase in network traffic, unusual outgoing network connections, system slowdowns, or unexpected behavior from network devices.


Similarly to their namesake from The Odyssey, Trojans are a kind of malware that masquerades as legitimate software or files but contains hidden malicious functionalities. They often enter systems through deceptive downloads, email attachments, or compromised websites. Once inside, Trojans can perform various actions, from stealing sensitive information and providing unauthorized access to systems to creating secret backdoors for use in future attacks.

Signs that a system may be under attack from Trojan malware include unexpected system behavior, unexplained network activity, the appearance of new files or processes, or the sudden disabling of security software.


Bots (or botnets) are networks of compromised computers controlled by an attacker, known as a “bot herder.” Bots typically infect systems through malware by exploiting vulnerabilities or through deceptive social engineering tactics. Once infected, the compromised devices become part of the botnet, allowing the attacker to remotely control and coordinate activities across the network of bots. Botnets can then be used to launch coordinated attacks, distribute spam emails, steal sensitive information, or carry out other malicious activities.

Identifying a bot infection may involve observing unusual network traffic, unexpected system behavior, increased network activity during idle periods, or a sudden surge in outgoing emails.


Spyware is a type of malware that covertly monitors user activities within a network or system, collects sensitive information, and relays it back to the attacker. It often enters systems through deceptive downloads, compromised websites, or bundled with legitimate software. Spyware can capture keystrokes, record browsing habits, collect personal information, and compromise user privacy.

Identifying spyware infections can be challenging as they are designed to remain silent as they observe and record user activities. However, some signs include a significant decrease in system performance, unexpected browser toolbars or extensions, or unexplained network activity.

Mobile malware

With the increasing prevalence of smartphones and other mobile smart devices, mobile malware has become a significant concern. Mobile malware targets mobile devices, compromising data, stealing personal information, and gaining control over the device. It can enter devices through malicious app downloads, compromised websites, or phishing attempts.

Identifying mobile malware can involve observing unusual battery drain on the mobile device, unexpected data usage, slow performance, sudden appearance of new apps, or unresponsive behavior.


Although not originally designed for illegal uses, rootkits are programs that have been co-opted as malware. These kits provide administrative access to a specific computer system, allowing the attacker to move freely and perform root-level functions without being challenged. As an added danger, rootkits are designed to completely conceal the user’s presence in the system.

While the attacker may be visible within the system, the presence of the rootkit itself can be discovered through a rootkit scan performed from a clean system. A memory dump analysis can also provide a clear picture of the instructions the rootkit is executing in the system.

How to Protect Yourself from Malware

Malware is diverse and pervasive, but there are steps you can take to protect your business. These strategies help create a more-comprehensive security layer around your sensitive data and vital networks, deflecting and mitigating malware attacks of all kinds. Regardless of the types of malware you are likely to encounter, consider doing the following:

Invest in the right software and security tools
Deploying a multi-layered approach to cybersecurity is essential. This includes using reliable antivirus and anti-malware software, firewalls, intrusion detection and prevention systems, and secure email gateways. For example, endpoint detection and response (EDR) solutions provide constant threat monitoring services while collecting vital security data on all network endpoints, and are capable of initiating threat response processes and alerting security teams after identifying potential threats. Regularly update your tools to ensure they can effectively detect and neutralize the latest malware threats.

Educate employees
Human error remains a significant factor in malware infections. Provide comprehensive training to employees on cybersecurity best practices, including recognizing and avoiding phishing emails, avoiding suspicious downloads and attachments, and recognizing unsafe browsing habits. Encourage a culture of cybersecurity awareness throughout your organization.

Keep all software and systems up to date
Regularly update operating systems, applications, and software with the latest security patches. Vulnerabilities in software can be exploited by malware to gain unauthorized access or execute malicious activities. Automated patch management systems can simplify this process and help ensure timely updates.

Regularly back up critical data
Create and maintain regular backups of important data. Store backups on separate systems or in offsite locations to protect against data loss in case of a malware infection or other security incidents. Test the backup and restore processes periodically to ensure their effectiveness.

Monitor network traffic and system logs
Implement effective network monitoring tools that can detect suspicious activities. Regularly review system logs and analyze network traffic to identify any anomalies or indicators of compromise. Promptly investigate and respond to potential security incidents to reduce the potential for damaged or compromised data.

Establish incident response and recovery plans
Develop comprehensive incident response and recovery plans to minimize the impact of a malware attack. This includes defining roles and responsibilities, outlining communication channels, and establishing procedures for containment, eradication, and system restoration.

Conduct regular security assessments and audits
Regularly assess and audit your organization’s security posture to identify potential vulnerabilities and areas for improvement. Engage third-party security professionals for independent assessments and penetration testing to identify and address any security weaknesses.

Stay informed about emerging threats
Stay updated on the latest trends and developments in the world of cybersecurity and malware. Follow industry news, subscribe to security alerts and advisories, and actively participate in relevant forums and communities to stay ahead of evolving malware threats.

Know Your Enemy

The evolution and proliferation of different types of malware is a major threat — financially, personally, and to society as a whole. Organizations of all sizes and in all industries need to familiarize themselves with the risk that these malware categories represent. Understanding the different types of malware and their characteristics is a crucial step in fortifying your organization’s defenses and staying ahead of potential cyberattacks. From the disruptive power of ransomware to the stealthy nature of rootkits, each type of malware presents unique challenges and requires specific countermeasures.

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