What is a Computer Worm? Everything You Need to Know (2023)

By Tibor Moes / Updated: June 2023

What is a Computer Worm? Everything You Need to Know (2023)

What is a Computer Worm?

Picture this: you’re at work, and suddenly your computer starts acting strangely. It’s slow, files are disappearing, and the network is grinding to a halt. You might have become a victim of a computer worm, a malicious program that can wreak havoc on businesses and individuals alike.

So buckle up as we dive into the world of computer worms, their impact on security, and the best prevention strategies to shield your systems from these silent invaders.


  • Computer worms are self-replicating malware that can spread quickly and autonomously across networks, causing harm or consuming resources.

  • They can cause damage such as data theft, system slowdowns, or creating backdoors for other malicious activities, like ransomware.

  • Preventing worms involves using up-to-date antivirus software, regular system patches, and safe internet browsing practices.

Don’t become a victim of cybercrime. Protect your devices with the best antivirus software and your privacy with the best VPN service.

Understanding Computer Worms: Definition and Function

So what exactly are computer worms? They’re a type of self-replicating malware that can spread through networks and infect computers without any human help. They can take advantage of software vulnerabilities or arrive as attachments in spam emails or messages, making them quite sneaky. Once installed, computer worms can modify and delete files, steal data, and even allow a hacker to gain control over a computer.

It’s like a snake slithering through your system, causing chaos wherever it goes. But what makes these digital serpents so effective at spreading? Let’s take a closer look at their self-replicating nature.

The Self-Replicating Nature of Worms

Computer worms have a unique ability to self-replicate, allowing them to spread rapidly across networks without any help from humans. They exploit vulnerabilities in networking protocols, like the File Transfer Protocol, to spread.

Think of them like a wildfire, spreading from one computer to another, and consuming everything in their path. This self-replicating nature is what sets computer worms apart from other types of malware like viruses, which need a host program to spread. It’s no wonder that computer worms can cause so much damage in such a short amount of time.

Damaging Effects of Worms

The consequences of a computer worm infection can be severe. They can include malicious attachments that can delete files or allow someone to take control of your computer remotely. Imagine your important documents vanishing before your eyes or your computer resources being hijacked by a hacker, like a puppet on a string.

Some of the most infamous worm incidents, such as the Morris Worm and WannaCry Ransomware Worm, caused significant data theft, file corruption, and system slowdowns. In the case of WannaCry, the worm even encrypted data and demanded a ransom payment, holding victims’ information hostage.

It’s clear that the damaging effects of worms can be far-reaching and devastating.

Differentiating Between Worms, Viruses, and Trojans

While computer worms are a unique type of malware, they’re not the only threats lurking in the digital world. Viruses and Trojans are two other common forms of malicious software, each with their own distinct characteristics and methods of infection.

Despite their differences, all three types of malware share a common goal: to cause harm and disruption. So, how can you tell them apart? Let’s explore the key differences between worms, viruses, and trojans to better understand their unique attack strategies.

Worms vs. Viruses

Viruses and worms may both be malicious programs, but they have a crucial difference in how they spread. Viruses require a host program to propagate and depend on human interaction to spread, such as opening an infected file or running a program.

On the other hand, computer worms are self-replicating programs that can spread across networks without human intervention. It’s like comparing a hitchhiker who needs a ride to spread (virus) versus a racecar driver who speeds from place to place on their own (worm).

This difference in spreading mechanisms makes worms particularly dangerous, as they can infect numerous systems in a short amount of time without any user interaction.

Worms vs. Trojans

Now that we’ve compared worms and viruses, let’s examine the differences between worms and trojans. While both can be malicious programs, trojans are a bit more deceptive. They masquerade as legitimate software, tricking the user into manually executing them. Once installed, trojans typically have a specific goal in mind, such as stealing data or giving hackers control over a system.

Unlike worms, trojans don’t usually try to infect other software or replicate themselves. Think of a Trojan as a wolf in sheep’s clothing, hiding its true intentions until it’s too late.

Understanding these distinctions is crucial in recognizing and protecting against these unique threats.

Notorious Computer Worm Incidents

Throughout history, there have been several high-profile computer worm incidents that serve as cautionary tales for the potential dangers of these malicious programs. These notorious attacks not only affected millions of users, but also caused significant financial and reputational damage to businesses and institutions.

Let’s dive into some of the most infamous computer worm incidents and their devastating consequences.

The Morris Worm

The Morris Worm holds the dubious distinction of being the first major computer worm incident. In 1988, Robert Tappan Morris Jr., a Cornell graduate student, unleashed the worm in an attempt to draw attention to network vulnerabilities and increase awareness.

However, due to a programming mistake, the worm quickly spread out of control, infecting up to 10% of the 60,000 systems connected to ARPANET, the precursor to the modern internet. This unintended consequence served as a wake-up call for the potential dangers of computer worms and the importance of securing networks against these threats.

WannaCry Ransomware Worm

In 2017, the WannaCry Ransomware Worm made headlines around the globe for its widespread and devastating impact. This malicious worm encrypted users’ data, locking them out of their computers unless they paid a ransom in Bitcoin. WannaCry spread rapidly by exploiting a vulnerability in the Windows operating system, infecting over 200,000 computers in more than 150 countries.

The attack caused significant disruption to businesses and institutions, including hospitals, which were forced to cancel surgeries and appointments due to inaccessible data. WannaCry remains a stark reminder of the potential dangers of computer worms and the importance of robust cybersecurity measures.

Types and Classification of Computer Worms

Computer worms come in various forms, each with its own unique spreading methods and payloads. From email worms to network worms, understanding the different types of computer worms is essential in recognizing and defending against these malicious threats.

Let’s examine some common classifications of computer worms and their distinct characteristics.

Email Worms

Email worms are a particularly sneaky type of computer worm that spreads through email attachments and messaging systems. These malicious programs often use social engineering tactics to trick users into opening the infected attachments, thereby allowing the worm to infect their system.

Once inside, the worm can replicate and spread to other users through the victim’s contacts, creating a snowball effect of infection. Staying vigilant and cautious with email attachments is crucial in defending against these devious digital threats.

Network Worms

Network worms are a type of computer worm that spreads through local area networks (LAN) or the internet. These malicious programs exploit weaknesses in the network, such as unpatched software or weak passwords, to infiltrate and propagate.

Some infamous network worms, like the Morris Worm and WannaCry, caused widespread damage and disruption by infecting thousands of systems in a short amount of time. Ensuring robust network security measures and keeping software up-to-date are essential in defending against network worm attacks.

Detecting and Removing Computer Worm Infections

So, how can you tell if your system is infected with a computer worm? And more importantly, how can you remove it? Detecting and removing computer worm infections can be challenging, but with the right tools and knowledge, you can safeguard your system against these malicious threats.

Let’s explore the common signs of a worm infection and the steps to take if you suspect your system is compromised.

Signs of a Worm Infection

There are several telltale signs that may indicate a possible worm infection. These include system slowdowns, unusual network activity, glitching, and abnormal pop-up messages.

Additionally, you might notice increased internet traffic or unexpected data transfers. Being aware of these symptoms and monitoring your system’s performance can help you detect a worm infection before it causes significant damage.

Steps to Remove a Worm

If you suspect your system is infected with a computer worm, the first step is to disconnect from the internet to prevent the worm from spreading further. Next, reboot your computer into Safe Mode with Networking by pressing the F8 key during startup.

Once in Safe Mode, run a thorough antivirus or anti-malware scan to detect and remove the worm from your system. In some cases, specialized worm-removal tools like Malwarebytes may be needed to eliminate the infection effectively.

Regularly scanning your system with updated antivirus software and following best practices for online safety can help prevent future worm infections.

Prevention Strategies for Computer Worms

Prevention is always better than cure; this is especially true when it comes to computer worms. Taking precautionary measures is key for thwarting virus attacks. Implementing robust prevention strategies can help protect your systems from these malicious threats and minimize the potential damage they can cause.

Let’s explore some best practices for safeguarding your systems against computer worm infections.

Regular Software Updates

Keeping your software up-to-date is crucial in reducing the risk of worms taking advantage of security flaws. Regular software updates not only fix bugs and improve performance, but also patch security vulnerabilities that may be exploited by worms.

Make it a habit to install operating system updates and security patches as soon as they become available to minimize potential attack vectors.

Antivirus Protection

Using reliable antivirus software with real-time protection and frequent updates is essential in defending against computer worm infections. These programs can help detect and block malicious code, safeguard sensitive data, and provide real-time protection against known threats and suspicious behavior.

Ensure that your antivirus software is updated regularly to stay one step ahead of emerging threats.

Safe Browsing Habits

Practicing cautious online behavior is another vital component of computer worm prevention. This includes avoiding suspicious links and attachments, only downloading software from reputable sources, and using strong, unique passwords for your accounts.

Additionally, consider using a firewall to block malicious traffic and prevent unauthorized access to your network. By adopting safe browsing habits and staying vigilant, you can reduce the risk of falling victim to computer worm infections.


In conclusion, computer worms are a formidable threat in today’s interconnected world. Their self-replicating nature, ability to spread without human intervention, and potential to cause significant damage make them a concern for both individuals and businesses alike. Understanding the different types of computer worms, detecting and removing infections, and implementing robust prevention strategies are crucial in safeguarding your systems from these malicious threats. By staying informed, vigilant, and proactive, you can protect your digital well-being and maintain a secure online environment.

How to stay safe online:

  • Practice Strong Password Hygiene: Use a unique and complex password for each account. A password manager can help generate and store them. In addition, enable two-factor authentication (2FA) whenever available.
  • Invest in Your Safety: Buying the best antivirus for Windows 11 is key for your online security. A high-quality antivirus like Norton, McAfee, or Bitdefender will safeguard your PC from various online threats, including malware, ransomware, and spyware.
  • Be Wary of Phishing Attempts: Be cautious when receiving suspicious communications that ask for personal information. Legitimate businesses will never ask for sensitive details via email or text. Before clicking on any links, ensure the sender's authenticity.
  • Stay Informed. We cover a wide range of cybersecurity topics on our blog. And there are several credible sources offering threat reports and recommendations, such as NIST, CISA, FBI, ENISA, Symantec, Verizon, Cisco, Crowdstrike, and many more.

Happy surfing!

Frequently Asked Questions

Below are the most frequently asked questions.

What is a computer worm in simple words?

In simple terms, a computer worm is a type of malicious software (malware) that can copy itself from one computer to another and spread across networks. It replicates itself quickly and does not require any human intervention to do so.

What does a computer worm do?

Computer worms are a form of malicious software designed to spread itself by replicating across multiple computers. It can do this without any human interaction and does not have to attach itself to another program or application in order to cause damage.

Computer worms can cause a variety of problems, including slowing down computer systems, corrupting data, and even deleting files. They can also be used to gain access to confidential information.

Can you get rid of computer worms?

Yes, you can get rid of computer worms. Most antivirus tools are designed to detect and remove them. Run a full virus scan to check your computer for any malicious code, then download a specialized worm-removal tool if needed.

Stay vigilant and keep your antivirus software up to date to prevent future infections.

Are computer worms harmful?

Computer worms can be harmful because they can spread malicious software or delete important files. They can also cause slower system performance, damage network hardware, and even access your personal information.

So yes, computer worms are harmful and should be avoided and removed.

Author: Tibor Moes

Author: Tibor Moes

Founder & Chief Editor at SoftwareLab

Tibor is a Dutch engineer and entrepreneur. He has tested security software since 2014.

Over the years, he has tested most of the best antivirus software for Windows, Mac, Android, and iOS, as well as many VPN providers.

He uses Norton to protect his devices, CyberGhost for his privacy, and Dashlane for his passwords.

This website is hosted on a Digital Ocean server via Cloudways and is built with DIVI on WordPress.

You can find him on LinkedIn or contact him here.

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