What is malware in computing?

Malware , short for malicious software, is any program designed to disrupt, damage, or gain unauthorized access to a computer system. Common types of malware include viruses, worms, trojans, spyware, and ransomware. It can infiltrate a computer through various means, such as email attachments, infected websites, or compromised software. Once installed, malware can cause a range of problems, from slowing down the device to stealing sensitive information or even taking complete control of the system.

How can malware affect a computer?

Malware , or malicious software, can harm a computer in various ways, including stealing data or running harmful code. Cybercriminals use it to extort money, steal personal information, and even spy on victims. Malware can disrupt system operations, resulting in denial of service by overloading systems with spurious requests. It can also tamper with system operations and cause data breaches like stealing credit card numbers. Types of malware include viruses, worms, and Trojan horses, which can spread rapidly and widely across networks, causing immense damage.

What are some common types of malware?

Malware is software designed to disrupt computer operations. Common types include: * Viruses replicate by inserting their code into other programs or files. * Worms spread across networks, exploiting vulnerabilities to infect systems. * Trojans are disguised as legitimate software but allow unauthorized access to systems. * Spyware secretly gathers personal information from a device. * Ransomware blocks access to data or devices, demanding payment for its release. * Adware displays unwanted advertisements on a user's device. * Scareware uses deceptive alerts to trick users into downloading more malware or providing sensitive data. * Rootkits are tools used to gain administrator-level access to a computer system.

How does malware typically spread to computers?

Malware spreads to computers through various methods, such as dangerous links, emails, and infected hardware devices. Cyberattackers may use strategies like "water holing," where they compromise webpages to attack visitors, or "baiting," where they leave malware in public online spaces. Often, malware is hidden within software packages, such as third-party apps or electronic games. Once installed, malware can cause a range of problems, from slowing down the computer to distributing pornography.

How can you protect your computer from malware attacks?

To protect your computer from malware attacks, be cautious of suspicious links or emails, as these are common methods for malware installation. Download software, especially electronic games or applications, only from trusted sources. Keep your operating system and security software updated to address vulnerabilities. Be wary of tactics like "baiting," where malware is left in public online spaces. Also, beware of scareware, which uses false alerts to trick you into downloading more malware or giving away information. Employing these measures alongside updated software can help defend against evolving cyber threats.

malware

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In full:: malicious software

Key People:: Leonard M. Adleman

Related Topics:: ransomware; list of notable computer viruses and malware; spyware; computer worm; zero-day malware

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malware

computing

Also known as: malicious software, malignant software

Written by

William L. Hosch

Fact-checked by

Britannica Editors

Last updated

Oct. 26, 2026 •History

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One AI model, trillions of variants: Breaking mass attacks on voice assistants • Oct. 17, 2026, 8:00 AM ET (Tech Xplore)

Top Questions

What is malware in computing?
Malware, short for malicious software, is any program designed to disrupt, damage, or gain unauthorized access to a computer system. Common types of malware include viruses, worms, trojans, spyware, and ransomware. It can infiltrate a computer through various means, such as email attachments, infected websites, or compromised software. Once installed, malware can cause a range of problems, from slowing down the device to stealing sensitive information or even taking complete control of the system.
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How can malware affect a computer?
Malware, or malicious software, can harm a computer in various ways, including stealing data or running harmful code. Cybercriminals use it to extort money, steal personal information, and even spy on victims.

Malware can disrupt system operations, resulting in denial of service by overloading systems with spurious requests. It can also tamper with system operations and cause data breaches like stealing credit card numbers. Types of malware include viruses, worms, and Trojan horses, which can spread rapidly and widely across networks, causing immense damage.
4 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What are some common types of malware?
Malware is software designed to disrupt computer operations. Common types include:
* Viruses replicate by inserting their code into other programs or files.
* Worms spread across networks, exploiting vulnerabilities to infect systems.
* Trojans are disguised as legitimate software but allow unauthorized access to systems.
* Spyware secretly gathers personal information from a device.
* Ransomware blocks access to data or devices, demanding payment for its release.
* Adware displays unwanted advertisements on a user's device.
* Scareware uses deceptive alerts to trick users into downloading more malware or providing sensitive data.
* Rootkits are tools used to gain administrator-level access to a computer system.
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Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How does malware typically spread to computers?
Malware spreads to computers through various methods, such as dangerous links, emails, and infected hardware devices. Cyberattackers may use strategies like "water holing," where they compromise webpages to attack visitors, or "baiting," where they leave malware in public online spaces. Often, malware is hidden within software packages, such as third-party apps or electronic games. Once installed, malware can cause a range of problems, from slowing down the computer to distributing pornography.
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1. malware
2. cyberattack: Malware
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How can you protect your computer from malware attacks?
To protect your computer from malware attacks, be cautious of suspicious links or emails, as these are common methods for malware installation. Download software, especially electronic games or applications, only from trusted sources. Keep your operating system and security software updated to address vulnerabilities. Be wary of tactics like "baiting," where malware is left in public online spaces. Also, beware of scareware, which uses false alerts to trick you into downloading more malware or giving away information. Employing these measures alongside updated software can help defend against evolving cyber threats.
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1. cyberattack: Malware
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

malware, malicious computer program, or “malicious software,” such as viruses, trojans, spyware, and worms. Malware typically infects a personal computer (PC) through e-mail, Web sites, or attached hardware devices. Mobile malware, including spyware and ransomware, attacks smartphones and tablets, often through text messages and mobile apps.

Malware may be used to take over PCs, turning them into zombie computers that may form part of a “botnet” used to send out spam or perform denial of service attacks on Web sites. In addition, malware has been used to distribute pornography and unlicensed software. Owners of infected PCs often become aware of a problem only as their machines become progressively slower or they find unidentifiable software that cannot be removed.

Rootkits are one of the worst forms of malware. Their name comes from the fact that they infect the “root-level” of a computer’s hard drive, making them impossible to remove without completely erasing the drives. In efforts to curb copyright infringement, some computer software makers and music companies secretly install detection software on users’ machines. For example, it was revealed in 2005 that the Sony Corporation had been secretly installing rootkits as its music CDs were loaded into PCs. The rootkit was discovered because of the way that it collected information on users’ PCs and sent the data back to Sony. The revelation turned into a public relations disaster, which forced the company to abandon the practice. The practice of monitoring users’ data, with or without installing rootkits, continues in the software industry.

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Britannica Quiz

Computers and Technology Quiz

The evolution of malware reached a new milestone in 2010, when the Stuxnet worm proliferated on computers around the world. Characterized as “weaponized software” by security experts, Stuxnet exploited four separate vulnerabilities in the Windows operating system to achieve administrator-level control over specialized industrial networks created by Siemens AG. By attacking these supervisory control and data acquisition (SCADA) systems, Stuxnet was able to cause industrial processes to behave in a manner inconsistent with their original programming, thus crossing the line between cyberspace and the “real world.” While Stuxnet’s intended target remained a matter of debate, the worm demonstrated that SCADA systems, which provide the backbone for such critical infrastructure sites as nuclear power plants and electrical grid substations, could be subverted by malicious code.

Another development in 2010 was the founding of the Israeli cyber-intelligence firm NSO Group for eavesdropping on mobile phones and harvesting their data. Its chief spyware, Pegasus, has been highly controversial, used to track politicians, government leaders, human rights activists, dissidents, and journalists. Although NSO Group claims its product is sold exclusively to government security and law enforcement agencies and only for the purpose of aiding rescue operations and battling criminals, such as money launderers, sex- and drug-traffickers, and terrorists, the spyware was used in 2018 by the Saudi Arabian government to track Saudi journalist and U.S. resident Jamal Khashoggi. Months before Khashoggi’s murder and dismemberment by Saudi agents in October 2018, Pegasus had been attached to the phone of Khashoggi’s wife. Facebook (now Meta Platforms) sued NSO Group under the United States Computer Fraud and Abuse Act in 2019, and two years later, Apple also sued. U.S. President Joseph Biden blacklisted the company in 2021, making it illegal for U.S. firms to sell technology to NSO Group.

William L. Hosch

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