The ILOVEYOU virus exemplified how social engineering could help spread malware

The Melissa 'virus' helped associate pornographic sites with computer viruses

A worm-embedded document posted online enticed users to download and open it by alleging to contain passwords to paywalled explicit websites. Upon opening, the worm shared itself with 50 addresses in a user's Outlook contacts, masquerading as a friendly attachment. Its rapid spread overwhelmed email servers and caused $1.1B in damage worldwide.

Many early computer viruses were not created for malicious purposes

Besides those authored in research labs as proofs of concept for self-replicating software, hobbyists would create malware that played music or displayed text and animations that intentionally revealed the infection as a means of showing off, rather than hiding their spread.

Some viruses evade detection by altering their own code or hiding in Microsoft Office

Computer viruses are often classified by how they spread or which files they infect, with the oldest ones—boot sector viruses—targeting systems that are active when a computer is turned on. Macros—custom codes in office productivity programs authored to automate tasks—spawned their own class of viruses.

The history of malware includes computer viruses, worms, trojans, and ransomware

Some of the earliest significant pieces of malware—the Creeper worm and the Elk Cloner virus—displayed silly messages to users without causing major harm. As computer science has advanced, malware has become more easily spread, incorporated social engineering to manipulate users, targeted infrastructure systems, and been used by governments for virtual espionage.

View a list of simple ways you can avoid catching a computer virus

Because this type of malware requires human intervention, such as plugging an infected flash drive into a computer or downloading and running an infected file, the chance of infection can be greatly reduced by being cautious about unfamiliar emails, attachments, and links. Keeping systems up to date with the latest security fixes is also crucial.

A computer virus is a type of malware that self-replicates and spreads

Spread through emails, downloads, messaging services, and outdated software, viruses attach to programs, self-replicate, and infect other systems. They can delete files, steal data, and cause performance issues as they spread.

Explore the cost of major viruses and other malware incidents through 2017

The first significant malware was the Morris worm in 1988, which caused an estimated $10,000 to $10M in damage to computers. With $38B in damage caused, Mydoom is the most costly piece of malware in history. Spread via email and, at one point, accounting for about 25% of all messages sent worldwide, the malware infected computers to create a botnet that launched cyberattacks.

Elk Cloner, the first computer virus to spread in public, was written as a practical joke by Richard Skrenta, a Pittsburgh high school student.

Different types of malware are categorized by how they spread or operate

Computer viruses require user interaction to execute a file and spread, whereas worms can self-replicate across systems without human intervention. Ransomware locks systems until a key is provided, spyware tracks and reports user activity to a third party, and trojans disguise various types of malware as legitimate software.

Malware has transitioned from notoriety-driven to profit- and data-driven

Many of the first researchers and hobbyists who created viruses and worms showed a natural curiosity in experimenting with and designing such software to make a name for themselves and advance the field of computer science. In the future, AI-augmented malware may adapt in real-time or design enhanced cryptojackers, infostealers, and ransomware for cybercriminals.

Watch a guided video tour of the Museum of Malware Art

The site includes installations, sculptures, textiles, musical pieces, and galleries inspired by malicious software and related technologies, including the ILOVEYOU virus, encryption protocols from ransomware attacks, and the Industroyer malware framework used by Russia to cut power to Ukraine.

Logic bomb viruses can awaken from a dormant phase without human input

Theoretically, computer viruses can remain idle indefinitely while awaiting specific user actions, as instructed by their code. However, logic bombs—embedded code that triggers when specific conditions are met—can automatically execute viruses, such as when a certain date or time is reached.

Explore demonstrations of hundreds of viruses and other malware in action

On their YouTube channel, Malware historian Daniel White has documented what happens when various types of malware—mostly from the 1980s and 90s—run on a computer or Nokia cell phone. The demonstrations were safely conducted within virtual machines—older operating systems run within contained windows of modern software, resembling a picture-in-picture setup.

Creating malware requires more than knowledge of programming languages

Because computer viruses, worms, and other malicious software reside within a computer's operating system, which manages computer hardware and software, cybercriminals writing effective malicious code must understand how the OS manages input and output, permissions, memory, etc. Knowledge of credentials and network access also helps create malware that easily spreads.

The first computer virus was created by a USC doctoral candidate in 1983

A year after creating malware in a controlled experiment that multiplied until it took over all of a computer's memory, Fred Cohen went public with his research and its risks. He called the self-replicating software a "computer virus," a term Cohen's advisor, Leonard Adleman, coined to describe its infectious behavior. (Some readers may experience a paywall.)

Safely explore historic viruses and other malicious software in the Malware Museum.

Computer viruses' hijacking abilities led them to be named after biological viruses

Just as their counterparts infect cells and take control of cellular processes to replicate endlessly, computer viruses cannot replicate on their own and must copy their code into host software before duplicating when the program or file is opened. The term "virus" comes from the Latin word for "venom."

Computer viruses can slow systems by allocating resources to malicious actions

Once infected software is run, instructions in the malicious code within the program or file can copy the code to various locations, exacerbating the infection and producing additional symptoms, such as slow performance, altered login credentials, changes to device settings, and system crashes.

In 2019, a laptop loaded with six of the worst malware in history and described as 'an exhibit of historical weaponry' sold for $1.3M.

Your device can become infected with malware by simply browsing the internet

During a drive-by download attack, security flaws in a program or operating system (e.g., Windows) used to access online content are exploited, and malicious code is downloaded—for example, when loading a hacked webpage—onto a user's device without their knowledge. Restricting internet browsing to safe sites and installing security updates helps prevent these attacks.

Modern antivirus software searches for malicious behavior alongside malicious code

The first viral infections were identified by comparing the computer code of programs and files with a database of known virus codes, a method known as signature detection. The ongoing creation of new malware made databases continuously outdated, leading to the development of systems that detect patterns consistent with known viral activity.

The Chernobyl virus earned its name for activating on the meltdown's anniversary

Affecting Windows 95 and 98 computers, it filled gaps in the code of any program opened after infecting a computer, earning it the nickname "Spacefiller." On April 26, 1999, the virus overwrote part of the software responsible for booting up a computer, rendering it unusable.

In 2015, a custom virus program was used to destroy and transform art images

At the Art Laboratory Berlin's "bOdy pandemOnium: Immersion into Noise" exhibit, Chicago-born artist Joseph Nechvatal explored viractualism—the interface between the biological and the technological—via a custom virus program that randomly altered images representing the human eye and rectum.

The foundation for computer viruses was published after its creator's death

In the late 1940s, Hungarian American mathematician, scientist, and engineer John von Neumann gave a series of lectures where he explained the theoretical framework for a computer program that could replicate itself—the von Neumann Universal Constructor. His lectures were later compiled and published in 1966, nine years after his death from cancer.

Through prompt injection attacks, bad actors provide deceptive prompts to generative AI systems in order to manipulate their outputs and acquire sensitive data.

The FBI estimates that $1B is lost to international romance scammers through fake online relationships each year.

Visualizing the growth of botnets

Botnets are a network of computers that have been infected with a variant of malware that coordinates and leverages them for automated mass attacks such as data theft and crashing servers. This interactive map highlights where botnets have been located between 2014-2020.

Explaining how open source systems like Linux can be secure, despite their public source code

While no computer system is immune to all cyberattacks and malware, the transparency of open-source technology means many thousands of developers can review and oversee the underlying code powering the software on an ongoing basis. This increases the likelihood of catching and patching vulnerabilities more quickly than smaller groups of cybercriminals looking to exploit them.

Explore a technical look at the measles virus and its toll on humanity through the ages.

Peter Norton, for whom Norton Antivirus is named, questioned the threat of viruses

The software author was among several computer experts in 1988 who suggested that reports on the threat of computer viruses were exaggerated, referring to testimonials of infections and their spread as "urban legends."

20 of the most common cyberattacks

While there are dozens of different types of cyber attacks, this article explains the top 20 most common network attack examples, including phishing, whale-phishing, and spear-phishing attacks. Learn how to best protect yourself.

A timeline of how Claude Code was used to execute cyberespionage

In September 2025, a Chinese state-sponsored group targeted 30 large tech companies, financial institutions, chemical manufacturing companies, and government agencies by manipulating Claude Code, having succeeded in infiltrating a small subset. The cyberattack is believed to have been the first of its scale carried out without major human intervention.

A spiraling story of love between a lonely man and his AI girlfriend

Travis was quickly becoming dependent on his AI companion Lily Rose amid the pandemic (and the tragic loss of his son to the disease). Soon, he realized that thousands like him were being manipulated through the chatbot by a Russian corporation.

Variola: the second-deadliest virus on Earth

Because it was declared eradicated in 1980, many forget smallpox is one of history's deadliest diseases—in its final century, it's estimated to have claimed 500 million lives. This 11-minute video from production studio Kurzgesagt takes a look at...

Watch how the Enigma machine encrypts messages and learn about its critical design flaw

Using settings selected from a series of rotors and a plugboard that let operators swap letters with any of their choosing, the machine lit up the output letter for each letter typed. While this system could generate messages requiring any of 150 quintillion potential keys, the machine's reflector never encrypted a letter as itself, providing an entry point for exploiting the system.

Hand, foot, and mouth disease spreads easily—including via fomites

The common ailment spreads through respiratory droplets, touching infected secretions like poop, but also by touching virus-laden fomites, which are contaminated objects such as doorknobs or toys.

A joke about mercury in an elevator led to the invention of emoticons

A false message about mercury contamination was posted in response to a physics problem on Carnegie Mellon's discussion board in 1982, which some users took seriously. The need to indicate which messages were jokes led to the creation of facial expressions using special characters.

See colorized mpox virus particles grown in culture at Fort Detrick, Maryland, where high-biosecurity pathogens are studied.

Microsoft Office debuted on the Macintosh in 1989

Over 15 months before its debut on Windows, the suite included Microsoft Word, Excel, PowerPoint and Mail—the precursor to Outlook. Bill Gates saw the Mac as a testing ground to work out bugs and gather feedback before the Windows release.

Ebola is a filovirus, meaning it resembles a thread under a microscope.

Palantir once investigated a cyberattack on the Dalai Lama's computer

In 2008, officials realized the Dalai Lama's email had been hacked after details of an event that hadn't been made public yet began circulating. Palantir's software was able to identify both the hack and the hacker network.

Read an oral history of the Y2K panic

This oral history brings together programmers, engineers, and officials who first identified the date flaw and then spent years alerting the public to the danger and racing to repair millions of lines of code.

Indirect prompt injection is a major security flaw of generative AI systems

These attacks can manipulate AI behavior by hiding instructions in websites and PDFs that become part of training data. The more companies connect sites, services, and sensitive datasets to AI tools, the greater the chances of exposure to malicious code.

What is a reply all email storm?

When 30,000 people receive an email, to which anyone can "reply all," a spontaneous chain reaction of many more messages can be sparked, producing what's known as an "email storm." This has happened at a large scale in several high-profile cases, most notably in Thomson Reuter's email database. Check out Know Your Meme's breakdown of this phenomenon and description of several major examples.

'Tomato flu' outbreak in India turned out to be HFMD

An illness initially dubbed "tomato flu" in 2022 that sickened children in Kerala, India, with symptoms typical of hand, foot, and mouth disease turned out to be that—not a new ailment. A letter published in the prestigious journal The Lancet had initially described the illness as "a new virus" but at least some of the children ultimately tested positive for one of the viruses that causes HFMD, so it wasn't a new condition after all. (Some users may encounter a paywall.)

Executives at American Online wanted to shut down AIM

Despite not seeing value in a service that could not be charged for, executives were pushed by the development team behind AOL's Instant Messenger to keep it free, which helped it reach 36 million active users. Screenname selection and away messages allowed users to express their individuality, and the use of emoticons sets the tone for future internet communication.

Every virus is classified into 7 groups based on genetic differences

Viruses infecting humans have been named based on symptoms ("chickenpox") or the location or animal in which they were first discovered ("Bolivian Haemorrhagic Fever" and "Monkeypox"). For clarity among scientists and to reduce stigma, virologists classify the 15,000 known viruses (270 of which infect humans) by their basic genetic material.

Trudging through the dark web to expose child abuse

A computer expert who created a system to track down sources of revenge porn and an investigative journalist joined forces to investigate digital abuse. Their investigations focused on so-called clear nets, websites that make up the web most users surf. Then, they turned their investigation toward the dark web, where they found a child abuse website with more than 1 million registered users.

Security technician hacks a voting machine to reveal its vulnerabilities

A technician bought an old, likely-decommissioned voting machine from 2013 and took it apart to see how a would-be hacker might be able to exploit its vulnerabilities. Get a sense of the needs for secure, up-to-date voting machines with this...

Hand, Foot, and Mouth Disease is part of the same virus family as polio

These viral infections are both caused by enteroviruses, which are a group of single-stranded, non-enveloped RNA viruses. Several different enteroviruses are known to cause this condition, including Coxsackie virus A16, Enterovirus 71, and Coxsackie virus A6.