A Computer Virus is a computer program which distributes copies of itself, even without permission or knowledge of the user. A computer virus is often simply called a virus if it is clear from the context that it does not refer to a biological virus. The term is commonly used to refer to a range of malware, but a true virus does not need to be harmful. To distribute itself, a virus needs to be executed or interpreted. Viruses often hide themselves inside other programs to be executed.