ruses, worms and Trojans are software programs that have been written by individuals to disrupt or interfere with your computer files. Viruses : Programs that can corrupt your software programs, disrupting the way they work, even how your computer functions. Worms : Specific types of viruses that spread copies of themselves to other computer systems (usually via network connections). Unlike typical viruses, worms do not generally infest your programs or operating systems, but greatly increase network or web traffic as they spread. Trojans : Specific types of viruses that seem harmless but can damage your computer files (like the mythical Trojan Horse) Unlike a true virus, Trojans can't reproduce themselves, nor can they infect your programs.