Programs such as viruses and worms designed to exploit weaknesses in computer software replicate and/or attach themselves to other software programs on a computer or a network. Because they are designed to cause harm to a computer’s or a network’s operation, viruses and worms are known as malicious code. In short, malicious code not only propagates itself but also typically causes damage to a computer system—such as denying access to legitimate users, altering or deleting data, or deleting complete file systems and disks.

See Also: Exploit; Virus; Worm.