The main types of malware include viruses, worms, trojans, ransomware, and spyware. Viruses attach themselves to legitimate software and spread when the program runs, while worms replicate independently across networks. Trojans disguise themselves as legitimate applications but perform harmful actions once executed. Ransomware encrypts user data and demands payment for its release, causing significant disruption. Spyware secretly collects user information, often leading to privacy breaches. Understanding these types helps in implementing effective cybersecurity measures.