Logic Bomb

Just like a real bomb, a logic bomb will lie dormant until triggered by some event. The trigger can be a specific date, the number of times executed, a random number, or even a specific event such as deletion of an employee's payroll record.

When the logic bomb is triggered, it will usually do something unpleasant. This can range from changing a random byte of data somewhere on your disk to making the entire disk unreadable. Changing random data may be the most insidious attack since it generally causes substantial damage before anyone notices that something is wrong. It's vital to have software in place that quickly detects such damage.

Although you can detect it after the fact, there is unfortunately no way to prevent a well written logic bomb from damaging your system.

If you've had someone in to do any system work on your computer (e.g., Y2K work) it's particularly important that you independently verify the work was done correctly and to verify no trap doors or logic bombs were inserted into your systems. Work like Y2K modifications require programmers to have detailed access to your systems; just the kind of access someone who wanted to insert a logic bomb into your system would love to have. (This is not to say Y2K contractors are worse than any other person who has low-level access to your systems; it's just one obvious example.) [Note: This was written before 2000 and all of the end-of-century hype; but the point is still just as valid today if you give control of your system to anyone. And, with today's remote desktop built into Windows; it's even easier to give such control over to a support person at some remote software vendor's location or someone posing as such.]