Keep Your PC Safe

A logic bomb is a malicious program which is inactive until a specific condition, or conditions, are met; the most common of which is a date. Frequently used dates to activate logic bombs are Friday 13th and April Fool’s day. As no malicious activity is encountered until the programmed conditions are met logic bombs are able to spread long before they are noticed or perceived to be a threat.

Conditions other than dates that may activate a logic bomb are many and varied but some of the most common are:
a) A special message on a particular website. The logic bomb may be programmed to check the website regularly and when the message appears the logic bomb strikes.
b) Certain activity on a PC such as installing or uninstalling a particular program. For example, the bomb may check for the presence of a certain screen saver and if the screen saver is ever uninstalled the logic bomb is activated.
c) It could be activated by something that doesn’t happen. For example, an employee may use a logic bomb that looks for that users activity on the system and if it does not occur for six weeks the bomb is activated. Such logic bombs are used to ‘punish’ the employee’s company for firing them.

Software companies which produce trial versions of their software that no longer work after the trial period are sometimes falsely considered logic bombs. True logic bombs have some form of malicious intent the use of logic to render trial software inactive cannot be described as malicious. It is only the software company protecting itself from users abusing the privilege of trying out the software.

A good anti-virus scanner, such as Kaspersky, that uses heuristics or logic when scanning for viruses can help keep your PC safe from logic bombs. This kind of virus scanner ‘reads’ a program and can detect if it could be dangerous to the PC.

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