Malware is malicious software designed to damage, disrupt, or gain unauthorized access to computer systems. Categories include viruses (attach to programs and spread), worms (self-replicate across networks), trojans (disguised as legitimate software), ransomware (encrypts data for extortion), spyware (covert surveillance), and rootkits (hide malicious activity).
Modern malware often combines multiple techniques, uses encryption to evade detection, and may be fileless—operating entirely in memory. Defense requires layered controls including patching, email filtering, endpoint protection, network monitoring, and user awareness.
CISSP Relevance
Malware concepts span Domain 7 (Security Operations) for detection and response and Domain 8 (Software Development Security) for preventing malware introduction. Understand malware types, infection vectors, detection methods, and response procedures. Know the difference between malware categories and appropriate countermeasures.
CISA tracks current malware threats at StopRansomware.gov.
Related terms: Phishing, Incident Response