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

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.

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Spread through emails, downloads, messaging services, and outdated software, viruses attach to programs, self-replicate, and infect other systems.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.

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."

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 The ongoing creation of new malware made databases continuously outdated, leading to the development of systems that detect patterns consistent with known viral activity.

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.

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.

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.

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.

The ILOVEYOU virus exemplified how social engineering could help spread malware

Displaying as LOVE-LETTER-FOR-YOU.TXT on Windows computers, the file appeared to be a love letter, which many users willingly opened. However, the file contained a script that damaged and hid files, caused Internet Explorer to download software to help steal passwords, and copied itself to all Outlook contacts to continue spreading.

Prompt viruses can exploit and take advantage of integrated AI systems

AI agents—software that can complete requested tasks without ongoing human direction—are expected to increasingly communicate with one another as users and businesses incorporate AI. Providing malicious, self-replicating instructions through prompt injection attacks can cause damaging commands to cascade across systems and services (e.g., banking), without requiring human intervention.

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

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.

Explore 3D models of some of the most dangerous viruses

Everyone has come in contact with common viruses—typically something like influenza (the common flu)—but sometimes they encounter more dangerous strains. While we're familiar with the symptoms that manifest, it wasn't until the advent of advanced microscopy that scientists could pin down the exact structure and behavior of various viruses.

Receptors on the cell surface are key to whether a virus is successful

Viral receptors are key regulators of host range, tissue tropism, and viral pathogenesis—basically, the door locks on cells allowing viruses to invade, if they have the right key. How this process works at the microscopic level determines whether a virus is able to trigger a widespread illness in the host.

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.

Seven known types of coronaviruses have jumped from animals to humans

Coronaviruses, including SARS-CoV-2, belong to a large family of viruses characterized by their crown-like appearance under a microscope, due to spike proteins on their surface. While thousands are believed to exist in animals, only seven are known to have made the jump to humans.

A technical look at the measles virus and its life cycle

The measles virus is made up of a single strand of RNA, packaged inside an envelope that varies in shape and size. A negative-sense paramyxovirus—the same family as mumps—the virus is encased in proteins that help it attach to immune cells inside the body.

Up to 8% of the human genome consists of ancient viral DNA

Human endogenous retroviruses are remnants of infections that affected human primate ancestors millions of years ago and were passed on by infiltrating sperm and egg cells. Studies have shown that this DNA may play a role in immune responses and in placental formation.

HFMD can survive on surfaces for days at a time

That's why the virus can be transmitted via fomites—surfaces that have virus on them like doorknobs, kids toys, etc. These viruses are resilient—they are often even resistant to freezing (and are frequently stored at freezing temperatures in lab settings).

Ebola is a filovirus, meaning it resembles a thread under a microscope, though it sometimes twists and can resemble a bowl of spaghetti.

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.

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.

Radioactive elements can introduce software errors because the ionizing radiation they produce can detach electrons from atoms, and computer code relies on the distribution of electrons.

Genetically modified viruses can help construct battery electrodes

MIT scientists' modifications caused the viruses to attract conductive materials, such as gold ions, which the viruses self-assembled into nanowires that could be used in batteries. These components allow batteries to be thinner and flexible enough to be constructed into new shapes.

Some employers are using new technology to surveil remote workers

'Bossware' tools help employers make sure their remote workers aren't slacking off on the job, using surveillance technology to monitor employee computer activity and more.

Most polio cases today are vaccine-derived rather than naturally occuring

Weakened, live virus vaccines—which aren't offered in the US—carry a risk of virus being shed in the stool. Rarely, the shed virus mutates and leads to vaccine-derived polio infections. Most recent polio cases are genetically linked to those vaccines. As shown in this graphic, there are typically hundreds of vaccine-derived polio cases annually.

Bacteria rapidly evolve (and share) new defenses against drugs they encounter

Unlike humans, bacteria rapidly make genetic changes in response to their environment, including creating defense against antibiotics. Furthermore, these defenses are passed on to their future generations and can even be shared with neighboring bacteria through horizontal gene transfer.

A vaccine against Epstein-Barr virus, researchers hypothesize, could potentially prevent MS

As many as a quarter of MS patients have antibodies in their blood that bind to both a central protein in Epstein-Barr virus and a protein made in the brain and spinal cord that—when attacked—leads to a breakdown of protective nerve fiber insulation. This suggests the immune system's primed to attack the nervous system after mounting a defense against Epstein-Barr.

Tattoos remain visible on your skin thanks to immune cells called macrophages

Visualize how CRISPR-Cas9—a type of immune system used by single-celled organisms to attack invasive viruses—targets and makes precise changes to a gene's DNA.

Experimental hantavirus vaccines and therapies, still under development, have long been funded by the US military.

When you complete a CAPTCHA on a website to prove you are human, you may be unknowingly training algorithms for self-driving cars, whose systems require training data to help identify crosswalks, bicycles, and other outdoor objects.

English mathematician Ada Lovelace wrote the first computer algorithm a century before computers existed and hypothesized that computing devices would one day be able to compose music—foreseeing the generative AI systems of today.

Memecoins are a type of cryptocurrency—a form of digital currency with a wide variety of uses—created around popular 'memes,' or viral internet jokes.

As of 2025, the most cited papers in science include a review of graphene, methods to improve image recognition, streamlining electron density calculations, and optimizing protein studies.

Track the location of the Voyager probes, currently between 13 and 15 billion miles away from Earth.

Some Pokémon have been named after real and fictional organisms, while some real-world species have been named after Pokémon, such as Chilicola charizard and Binburrum zapdos.

Animal phobias are likely the most common type of phobias, followed by an extreme fear of heights.

Poison ivy's rash-causing compound is found in the plant's roots, stem, and leaves—so coming into contact with any part of the plant can lead to rashes for the 85% of people who are allergic to it.

Venture capital is a form of funding provided to early-stage companies with high growth potential, typically in exchange for an equity (or ownership) stake

Gerrymandering works through two techniques: cracking opposing voters across districts to dilute their power, and packing them into a few to waste their votes in lopsided majorities.

Budweiser stores yeast derived from the original 1800s strain in a secret bunker, which only the Head of Yeast Management can access—not even the CEO

Volcanoes 'die' when their supply of magma runs out, if they are shifted away from their underlying magma reservoir, or if they get clogged by collapsing or their magma cooling back into rock.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

Planarian flatworms are small, aquatic worms with exceptional regenerative capabilities. When cut, the worms can regenerate multiple bodies in a matter of weeks.

Hear 50 years of iconic hip-hop samples, the genre's foundational looped tracks

Netflix profits when you're not watching, and its movies are designed that way—read a detail-rich critical essay exposing lesser-known Netflix takes

Calculate how much of your tax dollars go to each federal program based on your income, filing status, and number of children