Zero-click attacks can exploit device vulnerabilities in the background, without a user clicking anything, downloading or opening a file, or taking any other action.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 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.

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.

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.

Insecure devices connected to the Internet of Things pose risks to the entire network, which cybercriminals can hijack to compromise infrastructure and private resident data. Poorly secured systems that become inoperable can undermine the promise of smart cities by worsening the quality of life.

Browsing the dark web requires onion routing, which prevents visitors from being identified and the locations from which they connect from being traced. This has been useful to activists in environments affected by political oppression or instability. However, those unfamiliar with navigating the space may encounter malware and network attacks from denizen hackers.

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.

An easy-to-digest checklist on the many ways you want protect yourself from a cyberattack before it happens, if it happens, and after it happens.

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.

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.

Despite encrypting data and relaying it within the Tor network, traffic between the network exit and the final destination is no longer hidden and can be captured. Law enforcement agencies can also attempt to deanonymize users by monitoring and matching data signal patterns entering and leaving the network via a correlation algorithm.

It’s been a rough 10 years in cybersecurity—and it’s only getting worse. From the Stuxnet to the Sony Hack, learn about the worst cyberattacks over the last decade.

Cybersecurity researcher John Hammond explores the effectiveness of a dark web search engine, leaks from ransomware group data breaches, and a categorized index of dark web links, including some that are alleged to host malware. Many dark web sites are no longer active or host scams to fool unsuspecting visitors.

Using symmetric and asymmetric cryptography, data is encrypted on the sender's device before being transmitted across application servers that lack the key needed to decrypt it. The message is not decrypted until it reaches the recipient's device, which uses their private key to recover the plaintext. E2EE's effectiveness has led to its adoption by WhatsApp and Signal.

A mix of centralized cloud infrastructure and legacy protocols leaves the internet susceptible to downtime from minor cyberattacks or software bugs, infrastructure damage caused by extreme weather, and human error if a DNS service provider—the internet's phone book—or a backend system, such as Amazon Web Services, were compromised.

A suite of cutting-edge hardware and computation-intensive software creates the potential for self-driving cars to be safer, more fuel-efficient, and more accessible to a broader range of drivers. However, automation also introduces potential cybersecurity threats.

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...

Smart cities require vast troves of data to run, making their systems attractive to hackers. Listen to this one hour podcast to learn about the risks and what is being done to mitigate them.

By using a network of devices, including digital meters, sensors, and controllers, smart grids can quickly detect mechanical issues and fluctuations in supply and demand, automatically adjusting electricity flow to prevent cascading failures. While this is important for variable solar and wind power generation, many of these computer systems are designed to be controlled remotely, which increases the risk of malicious access.

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.

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.

Smart cities utilize massive datasets to enhance mobility, resource utilization, and public safety. However, this data can also be compromised if mishandled by residents, making citizen awareness of risks a key component of cybersecurity efforts.

Currently, technology exists to scrape and download data from webpages, which can then be analyzed to identify a user's information. However, scrapers cannot access or remove personal data from dark websites because they are often protected by paywalls, rendering monitoring ineffective beyond reporting publicly available data breaches.