malware

A program that is inserted into a system, usually covertly, with the intent of compromising the confidentiality, integrity, or availability of the victim’s data, applications, or operating system or of otherwise annoying or disrupting the victim. Source: NIST.gov

Many people infect their devices with malware by falling for scams, opening bogus attachments and through irresponsible technology use (e.g. downloading copyrighted materials for free).