Computer Virus

A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user. The original may modify the copies or the copies may modify themselves. A virus can only spread from one computer to another when its host is taken to the uninfected computer, for instance by a user sending it over a network or carrying it on a removable medium such as a floppy disk, CD, USB drive or by the Internet. Additionally, viruses can spread to other computers by infecting files on a network file system or a file system that is accessed by another computer. Many personal computers are now connected to the Internet and to local-area networks, facilitating the virus to spread using the system

Some viruses are programmed to damage the computer by damaging programs, deleting files, or reformatting the hard disk while some are not designed to do any damage, but simply replicate themselves and make their presence known by presenting text, video, or audio messages. Even these gentle viruses can create problems for the computer user. They typically take up computer memory used by legitimate programs. As a result, they often cause erratic behavior and can result in system crashes. In addition, many viruses are bug-ridden, and these bugs may lead to system crashes and data loss.