What Are Malware, Viruses, and Spyware — and How Do They Differ?
Virus A computer virus is malicious code that attaches itself to legitimate programs or files. It spreads when those programs are executed, replicating itself and potentially damaging systems, corrupting data, or disrupting normal operations.
Worm A worm is self-replicating malware that spreads independently across networks, without needing a host program. It often propagates through email, USB devices, or system vulnerabilities, consuming resources and degrading system or network performance.
Trojan (Trojan Horse) A Trojan is malware disguised as a legitimate or useful application. Once installed, it can give attackers control of the system, often leading to the installation of additional threats such as backdoors or keyloggers.
Keylogger A keylogger secretly records keystrokes, capturing sensitive information such as passwords, credit card numbers, and login credentials without the user’s knowledge.
Backdoor / Bot A backdoor is a hidden method of bypassing normal authentication to gain unauthorized access to a system. Once compromised, the device may become a “bot,” allowing attackers to remotely control it as part of a larger botnet.
Exploit An exploit is a tool or piece of code that takes advantage of vulnerabilities in software or operating systems, allowing attackers to gain partial or full control of a system.
Spyware Spyware secretly collects user data—such as browsing habits, credentials, or personal information—and transmits it to third parties without consent.
Adware Adware displays unwanted advertisements, often bundled with free software. While not always harmful, excessive ads can degrade performance and may expose users to additional security risks.
Rootkit A rootkit is a set of tools designed to gain and maintain unauthorized access while remaining hidden. It often conceals malicious processes and can be extremely difficult to detect or remove.
Rogue Software / Scareware Rogue security software pretends to be legitimate antivirus or anti-spyware protection. It uses fake alerts and warnings to scare users into purchasing fraudulent software.
Ransomware Ransomware encrypts files or locks a system, demanding payment (often anonymously) to restore access. It is one of the most financially damaging types of malware.
