Viruses are a specific type of malware: malicious software programs that replicate themselves by modifying software with their own code once they've invaded. Anything that can harm your devices or steal your personal information is included in the malware category. Malware is short for malicious software and includes Trojan horses, spyware apps, and viruses. The term virus has entered the common vernacular to mean any unwanted invader of a computer or handheld device, but if we're technical, there is a difference between a virus and malware.