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Logic Bombs

A logic bomb is code that has, in some way, been inserted into software; it is meant to initiate one of many types of malicious functions when specific criteria are met. Logic bombs blur the line between malware and a malware delivery system. They are indeed unwanted software but are intended to activate viruses, worms, or Trojans at a specific time. Trojans set off on a certain date are also referred to as time bombs. The logic bomb ticks away until the correct time, date, and other parameters have been met. So, some of the worst bombs do not incorporate an explosion whatsoever. The logic bomb could be contained within a virus or loaded separately. Logic bombs are more common in the movies than they are in real life, but they do happen, and with grave consequences; but more often than not, they are detected before they are set off. If you, as a systems administrator, suspect that you have found a logic bomb, or a portion of the code of a logic bomb, you should notify your superior immediately and check your organization’s policies to see if you should take any other actions. Action could include placing network disaster recovery processes on standby; notifying the software vendor; and closely managing usage of the software, including, perhaps, withdrawing it from service until the threat is mitigated. Logic bombs are the evil cousin of the Easter egg.

Easter eggs historically have been a platonic extra that was added to an OS or application as a sort of joke; often, it was missed by quality control and subsequently released by the manufacturer of the software. An older example of an Easter egg is the capability to force a win in Windows XP’s Solitaire by pressing the Alt+Shift+2 keys simultaneously. Easter eggs are not normally documented (being tossed in last minute by humorous programmers) and are meant to be harmless, but nowadays they are not allowed by responsible software companies and are thoroughly scanned for. Because an Easter egg (and who knows what else) can possibly slip past quality control, and because of the growing concerns about malware in general, many companies have adopted the idea of Trustworthy Computing, which is a newer concept that sets standards for how software is designed, coded, and checked for quality control. Sadly, as far as software goes, the Easter egg’s day has passed.


Published on Sun 12 April 2009 by Elliot Wood in Security with tag(s): logic bombs malware