A Logic Bomb is a piece of often-malicious code that is intentionally inserted into software. It is activated upon the host network only when certain conditions are met.
Logic bombs execute their functions, or launch their payload, once a certain condition is met such as upon the termination of an employee. This makes their presence undetected until it executes their function, which can range from inflicting harm through files deletion and self-propagation. Logic bombs can also take effect on the target system upon a certain date — e.g. 2000, Y2K — and these are termed time bombs.
“Some disgruntled developers have a way of ‘going out screaming’ when they leave or are terminated from a work setting. They insert logic bombs into company systems that, upon certain events or at certain times, execute malicious functions such as files deletions.”