Malware Examples (2024): The 7 Worst Attacks of All Time

By Tibor Moes / Updated: May 2024

Malware Examples (2023): The 14 Worst Attacks of All Time

Malware, or malicious software, poses a significant threat to the digital world, compromising personal and organizational security on a global scale.

In this article, we will explore the seven most devastating malware attacks in history, revealing their impact and the lessons learned from each.


Malware, short for malicious software, encompasses a range of software designed to disrupt, damage, or gain unauthorized access to computer systems.”

  • Morris Worm (1988): An early example of a computer worm, it rapidly infected a significant portion of the internet’s computers within a day. Approximately 6,000 out of 60,000 connected computers were hit, with damages soaring into the millions.
  • ILOVEYOU Worm (2000): This worm spread through email, deceiving users with a love letter attachment. It infected over 10 million Windows PCs.
  • Code Red Worm (2001): Targeting computers with Microsoft’s IIS web server, this worm infected over 359,000 systems in less than 14 hours. The estimated damage was over $2 billion.
  • Mydoom (2004): Known for its massive scale, this virus spread primarily via email. It caused an estimated $38 billion in damages, infecting around 50 million computers.
  • Stuxnet (2010): A sophisticated cyber weapon targeting Iran’s nuclear facilities, it impacted physical infrastructure. It infected over 200,000 computers and led to the degradation of 1,000 machines.
  • WannaCry (2017): A ransomware attack of unprecedented scale, it affected around 200,000 computers across 150 countries. The estimated global financial loss from this attack was up to $4 billion.
  • Shlayer (2018): A significant threat to macOS users, this Trojan disguised as a legitimate download. It affected 10% of Macs analyzed by Kaspersky.

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Malware Examples

1. Morris Worm (1988)

In 1988, the digital world witnessed a groundbreaking yet alarming event with the emergence of the Morris Worm. This early form of computer worm quickly became notorious for its rapid spread and extensive damage.

According to the FBI, within a mere 24 hours of its release, an astounding 6,000 computers were infected – a significant number considering the relatively small size of the Internet at that time, which consisted of only about 60,000 connected machines.

The financial impact of this attack was initially estimated to be around $100,000, but as the extent of the damage became clearer, these figures dramatically escalated into the millions.

The Morris Worm was a wake-up call, highlighting the vulnerability of networked systems and setting a precedent for the need for improved cybersecurity measures.

2. ILOVEYOU Worm (2000)

Fast forward to the year 2000, and the digital world encountered a new, more sophisticated threat – the ILOVEYOU Worm. This particularly invasive malware took advantage of human curiosity and trust, spreading through email with the lure of an affectionate message. reports that this worm was alarmingly successful, infecting over 10 million Windows personal computers starting from May 5, 2000. The simplicity of its method – a seemingly harmless email attachment – coupled with its wide reach, marked a new era in the sophistication of cyber threats.

The ILOVEYOU Worm not only caused substantial economic damage but also served as a stark reminder of the evolving nature of malware and the importance of caution in digital communication.

3. Code Red Worm (2001)

In the summer of 2001, a new kind of cyber threat emerged, known as the Code Red Worm. This malicious software rapidly garnered notoriety due to its unprecedented speed and reach.

According to a study by David Moore, Colleen Shannon, and Kimberly C. Claffy, Code Red managed to infiltrate over 359,000 systems in less than 14 hours. This astonishingly quick proliferation highlighted a new level of threat posed by network-based worms.

The worm targeted computers running Microsoft’s IIS web server, exploiting a known vulnerability, and its impact was monumental. The total financial damage inflicted by the Code Red Worm was estimated to be in excess of $2 billion.

This event not only emphasized the need for timely software updates and patches but also marked a significant point in cybersecurity history, showing how quickly new malware could spread across the globe.

4. Mydoom (2004)

In 2004, the digital world faced another massive cyber threat: Mydoom. This worm, recognized for its record-breaking impact, caused widespread havoc and is still remembered as one of the worst viruses in history.

According to Nordvpn, Mydoom was responsible for a staggering $38 billion in damages. Its method of spread was primarily through email, using deceptive tactics to trick users into executing the malicious attachment.

Security researchers estimate that Mydoom infected around 50 million computers worldwide, making its reach and impact unparalleled at the time.

The scale of this attack underscored the evolving sophistication of malware creators and the importance of robust digital security practices. Mydoom’s legacy is a testament to the ever-present need for vigilance and preparedness in the face of evolving cyber threats.

5. Stuxnet (2010)

Stuxnet, emerging in 2010, marked a significant evolution in the world of cyber warfare. This sophisticated worm was not just another piece of malware aimed at stealing data or causing disruptions; it was a weapon specifically designed to target and sabotage physical infrastructure.

As reported by M.A.C Solutions, Stuxnet had a particularly devastating effect on Iran’s nuclear program, damaging nearly one-fifth of the country’s nuclear centrifuges. It accomplished this by infecting more than 200,000 computers and causing physical degradation in 1,000 machines that were crucial to Iran’s nuclear activities.

The precision and complexity of Stuxnet’s design set a new benchmark in cyber warfare, demonstrating how digital tools could be used to achieve strategic geopolitical objectives. This incident not only raised global awareness about the vulnerabilities of industrial control systems but also prompted a reevaluation of cybersecurity strategies in critical national infrastructures.

6. WannaCry (2017)

In 2017, the world witnessed one of the most widespread and damaging cyberattacks in history – WannaCry. This ransomware attack, as reported by, was unprecedented in its scale, affecting approximately 200,000 computers across 150 countries. Europol described the campaign as an extraordinary event due to its global reach and rapid spread.

WannaCry locked users out of their data, demanding a ransom to regain access, causing panic and chaos in various sectors, including healthcare, finance, and government. The economic and financial impact of WannaCry was enormous, with estimated losses reaching up to $4 billion.

This attack served as a stark reminder of the critical importance of cybersecurity in a highly interconnected world and highlighted the need for regular software updates, robust backup strategies, and international cooperation in combating cyber threats.

7. Shlayer (2018)

In 2018, the cybersecurity landscape for macOS users changed dramatically with the emergence of the Shlayer Trojan. This malware challenged the long-standing perception that Mac systems were largely immune to the kind of security threats frequently encountered on Windows platforms.

As reported by, by 2019, the Shlayer Trojan had become the most common threat for macOS users. A startling statistic from Kaspersky revealed that 10% of all Macs analyzed were affected by this Trojan, underscoring its widespread impact.

Shlayer was particularly insidious because it disguised itself as a legitimate software update or download, tricking users into installing it. Once installed, it bombarded users with an onslaught of adware and potentially unwanted programs. This not only compromised the user experience but also exposed users to further security risks.

The prevalence of Shlayer served as a critical wake-up call to the Mac community, highlighting the importance of vigilance even in a relatively secure ecosystem. It reminded users and developers alike that no system is impervious to attack and that maintaining cybersecurity is a continuous and evolving challenge.


This article has chronicled some of the most devastating malware attacks in history, each illustrating the evolving nature and increasing sophistication of cyber threats.

From the Morris Worm’s pioneering spread in 1988 to the widespread disruption caused by WannaCry in 2017, these examples highlight the continuous and ever-growing threat posed by malware. They serve as stark reminders of the importance of cybersecurity vigilance and the need for effective measures to safeguard digital assets.

In light of these threats, particularly for users of the latest operating system like Windows 11, the importance of investing in reliable antivirus software cannot be overstated. Leading brands such as Norton, Avast, TotalAV, Bitdefender, McAfee, Panda, and Avira offer comprehensive solutions that provide essential protection against a wide range of malware.

These tools not only help in detecting and removing viruses but also play a crucial role in preventing potential attacks. In an era where digital threats are increasingly sophisticated, having a robust antivirus software is an indispensable component of any cybersecurity strategy.




Author: Tibor Moes

Author: Tibor Moes

Founder & Chief Editor at SoftwareLab

Tibor has tested 39 antivirus programs and 30 VPN services, and holds a Cybersecurity Graduate Certificate from Stanford University.

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

You can find him on LinkedIn or contact him here.