The common types of malware vary by how they infect the system and what they intend to do.
Trojans hide malicious code in legitimate-looking applications. These programs typically have a single function and do not replicate.
Adware and Scareware deliver unsolicited ads and pop-ups that try to persuade users to make unnecessary purchases.
Spyware operates in the background of a system to gather sensitive data.
Ransomware encrypts files when it executes. The sponsoring organization demands a payment to decrypt the files.