- There are three most commonly encountered malicious programs - computer viruses , trojan horses and logic bombs
- Computer viruses act like biologics in the way they can be set off : they can be virulent from the outset of the infection or they can be activated by a specific event ( logic bomb )
- a set of instructions inserted into a program that are designed to execute (or `explode'') if a particular condition is satisfied; when exploded it may delete or corrupt data, or print a spurious message, or have other harmful effects; "a disgruntled employee planted a logic bomb"
A logic bomb is a piece of code intentionally inserted into a software system that will set off a malicious function when specified conditions are met. For example, a programmer may hide a piece of code that starts deleting files (such as a salary database trigger), should they ever be terminated from the company.