What is Logic Bomb

                 Logic bombs are small programs or sections of a program triggered by some event such as a certain date or time, a certain percentage of disk space filled, the removal of a file, and so on. For example, a programmer could establish a logic bomb to delete critical sections of code if she is terminated from the company. Logic bombs are most commonly installed by insiders with access to the system.
                The most common activator for a logic bomb is a date. The logic bomb checks the system date and does nothing until a pre-programmed date and time is reached. At that point, the logic bomb activates and executes it's code.A logic bomb could also be programmed to wait for a certain message from the programmer. The logic bomb could, for example, check a web site once a week for a certain message. When the logic bomb sees that message, or when the logic bomb stops seeing that message, it activates and executes it's code

                A logic bomb can also be programmed to activate on a wide variety of other variables, such as when a database grows past a certain size or a users home directory is deleted.The most dangerous form of the logic bomb is a logic bomb that activates when something doesn't happen. Because a logic bomb does not replicate itself, it is very easy to write a logic bomb program.In some ways, a logic bomb is the most civilized programmed threat, because a logic bomb must be targeted against a specific victim.

                   Imagine a suspicious and unethical system administrator who creates a logic bomb which deletes all of the data on a server if he doesn't log in for a month. The system administrator programs the logic bomb with this logic because he knows that if he is fired, he won't be able to get back into the system to set his logic bomb.

                   Logic bombs also can be created to simply alter some data in random ways that have no benefit to the author but damage the organization. For example, changing one cell in a large spreadsheet can have damaging effects on some forecast or analysis that affects the organization's future.

                  Programmers also can use logic bombs to ensure that they are paid for their work. A programmer in Waukesha, Wisconsin, wrote software for a client. When the client refused to pay for the software, the programmer pulled the pin. The programmer claims he was merely repossessing his own property -_ the copyright he held. The client makes the usual claims that the programmer's action damaged the business and that the code had bugs. The trial goes forward at this writing.