A virus is a kind of malicious code or program that, when executed, duplicates itself by modifying other computer system programs and inserting its own code. When this duplication is successful, the affected locations are then said to be contaminated with a virus.
Viruses frequently spread by producing a copy of themselves on a user's computer without the user's knowledge or consent. In a lot of cases, viruses will be spread by email accessories or by files shared on peer-to-peer networks. Once an infection has infected a computer system, it can infect other computer systems on the same network.
click to find out more Some viruses are programmed to spread themselves in such a way that could trigger major damage to a computer system. For example, an infection might erase files, fill a hard drive with useless data, or corrupt system files. In many cases, an infection may even show a message or image that is created to scare the user.
A lot of infections are reasonably harmless, and only cause small annoyance to the user. However, some viruses can be extremely dangerous, and can cause prevalent damage to computer systems.