Computer Viruses A virus is a program that copies itself without the knowledge of the computer user. Typically, a virus spreads from one computer to another by adding itself to an existing piece of executable code so that it is executed when its host code is run. If a virus if found, you shouldn't panic or be in a hurry, and you should work systematically. Don't rush! A Viruse may be classified by it's method of concealment (hiding). Some are called stealth viruses because of the way that they hide themselves, and some polymorphic because of the way they change themselves to avoid scanners from detecting them. The most common classifica