What is a malware software? How it causes? Is it a virus? How it occurs and what type of a harm can it do? How to get rid of that?

Malware - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Malware)

Malware, short for malicious software, is software designed to infiltrate a computer system without the owner's informed consent. The expression is a general term used by computer professionals to mean a variety of forms of hostile, intrusive, or annoying software or program code.[1] The term "computer virus" is sometimes used as a catch-all phrase to include all types of malware, including true viruses.
Software is considered malware based on the perceived intent of the creator rather than any particular features. Malware includes computer viruses, worms, trojan horses, most rootkits, spyware, dishonest adware, crimeware and other malicious and unwanted software. In law, malware is sometimes known as a computer contaminant, for instance in the legal codes of several U. S. states, including California and West Virginia.[2][3]
Malware is not the same as defective software, that is, software that has a legitimate purpose but contains harmful bugs.
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