Common Malware Types and Examples

In this article

Common Malware Types and Examples

• Virus

• Worm

• Trojan

• Ransomware

• Spyware

• Adware

• Botnet

• Fileless Malware 

• A Short History of Malware Development 

• Malware Prevention Challenges 

• Disguised Malware

• Signature-Based Detection Is Not Enough

• Sandboxing Is Inefficient

• How Anti-Malware Technology Works 

• Signature-Based Malware Detection

• Behavior-Based Malware Detection

• Recursive Unpacking

• Next-generation Sandboxing 

• Malware Attacks Protection and Prevention Best Practices

• Install Anti-Malware Software

• Keep Software Updated

• Secure Browsers

• Regulate Networking and Storage

• Implement Email Security and Spam Protection

• Preventing Malware with Perception Point

• See Our Additional Guides on Key Hacking Topics

• Ransomware

• Phishing

• Cloud Security

• Common Malware Types and Examples

• Virus

A computer virus is malicious software that, once activated, copies itself from one folder to another and inserts its own code. Viruses can spread quickly and can infect systems to steal personal and financial information, send spam, or lock users out of their devices.

Worm

Worms are very similar to viruses in that they replicate themselves within a system, but unlike viruses, they cannot infect other programs. Once installed, the worm starts running silently, infecting computers without the user’s knowledge. Worms can replicate themselves hundreds of times, consuming system resources and damaging devices.

Trojan

A Trojan Horse is a type of malware that masquerades as legitimate software but is actually used for malicious purposes. Trojans claim to be free updates, games, or antivirus programs and can trick users into installing them on their devices. Once installed, Trojans run silently in the background to steal important data, install backdoors and perform other harmful activities.

Ransomware

Ransomware has massively grown in recent years and causes damage estimated at more than $8 billion worldwide by the end of the year. Ransomware is malware that encrypts a victim’s data and blocks access until a ransom is paid. The most common way ransomware is delivered is by clicking on a link in an email or opening a malicious attachment.

Spyware

Spyware is software that is installed on a device and secretly monitors a victim’s online activities. It collects data such as passwords, credit card numbers, and browsing activity.

Adware

Adware is malicious software that, once downloaded, displays unwanted advertisements on victims’ computers. Adware doesn’t always do immediate damage, but it can be very annoying as it leads users to unwanted advertisements, opens intrusive pop-up windows, and might redirect users to malicious sites.

Botnet

A bot is a malware-infected device that performs harmful tasks without the user’s knowledge. A botnet is a network of infected devices working together under the control of an attacker. Botnets can be used to conduct phishing campaigns, send spam, or conduct distributed denial-of-service (DDoS) attacks.

Fileless Malware 

Fileless malware is malicious software that does not rely on download of malicious files. Instead, it uses legitimate programs to infect a system. It is hard to detect and remove, because it only operates in memory and does not leave any footprint on the target system. 

Fileless malware is a powerful type of attack that can evade most security tools—only behavioral analysis and other advanced techniques can identify and address them. 

A Short History of Malware Development 

1980s: The Morris worm

One of the first and most prominent malware incidents in history was the Morris worm, introduced in 1988. Developed in academia, it could spread to other systems over a network, primarily by exploiting vulnerabilities in software called sendmail which was then commonly deployed on computers. The worm did not check whether the target system was already infected. It created multiple copies of itself on each system, consuming all system resources of the victim and rendering them unusable. 

1990s: The first hacker communities

The Morris worm showcased the power of malware, and led to the first conviction for malware development. Since then, many other types of malware have emerged. In the 1990s, computers became more ubiquitous and affordable to the general public, and the first hacker communities began to develop worldwide. 

Gradually, their focus shifted to making money. Programming started to be taught in schools and universities, and new high-level programming languages were created, making it easier for inexperienced people to start writing code. The same skills were exploited by criminals to write malicious code. 

2000s: Organized cybercrime and economically motivated threat actors

Over the next decade, malware development has become a lucrative and organized illicit activity. Specialized cybercrime organizations with clearly defined responsibilities began to emerge. 

Many of these groups focused on attacking individual computer users and stealing funds or carrying out fraud. They used all available money laundering methods, initially using money mules and later turning to cryptocurrencies to avoid being tracked. These groups are often referred to as economically motivated threat actors.

2010-2020s: Ransomware and the shift to larger targets

In recent years, the focus of cybercriminal groups has gradually shifted from attacking consumers or small businesses to bigger and more attractive targets—large institutions. The most common example is using ransomware to encrypt an organization’s files before demanding a ransom to restore access. Modern attacks make use of double extortion tactics—threatening either to encrypt files or to release sensitive material to the public.

State sponsored malware

Governments are also making use of malware for cyberespionage and cyberwarfare. The Stuxnet attack, which was used to sabotage Iranian nuclear centrifuges, gained public attention due to its ability to cause physical destruction. Malware development groups involved in this process are often state-sponsored. In addition, some companies openly develop advanced surveillance malware and sell it to governments. One example is NSO Group, which sells the Pegasus threat.

Malware targeting popular computing platforms

Malware tends to have best coverage on the most popular computing platforms. On desktop and laptop computers, Windows-based systems have the most malware threats. In the mobile market, Android is the market leader and is the target of most malware families. Finally, Internet of Things (IoT) malware is on the rise, targeting poorly secured smart devices, which are mostly Linux-based.