Malware is malicious software designed to infiltrate, damage, or exploit computer systems and networks without the user’s consent. Types of malware include viruses, worms, trojans, ransomware, and spyware. Once installed, malware can steal sensitive information, disrupt operations, encrypt data for ransom, or give access to the unauthorized. Protecting against malware involves using antivirus programs, firewalls, regular software updates, and user education to recognize and avoid malicious threats.