For a listing of all articles on this site, click here . A piece of programming code, not part of the original code, inserted into an executable program.
Viruses behave in different ways.
Some viruses stay active in memory until you turn off your computer. Other viruses stay active only as long as the infected software program is running. Turning off your computer or closing the software program removes the virus from memory, but does not remove a virus from an infected file or disk. Viruses don't necessarily let you know that they are there even after they do something destructive. The vast majority of viruses are benign and will cause little if any damage.