From the WareGlossary

Malware: software that contains malicious programming

From Wikipedia

Malware (a portmanteau of "malicious software") is software program designed to fulfil any purpose contrary to the interests of the person running it. Examples of malware include viruses and trojan horses.

Malware can be classified based on how it is executed, how it spreads, and/or what it does. The classification is not perfect, however, in the sense that the groups often overlap and the difference is not always obvious, giving rise to frequent flame wars. read more