What term best describes malicious software that warns of deleting files when a specific event occurs, such as an employee's termination?

The term that best describes malicious software designed to trigger a harmful action, such as deleting files when a specific event occurs (like an employee's termination), is a logic bomb. A logic bomb is a piece of malicious code that is programmed to execute a specified action when certain conditions are met.

In this case, the condition is the termination of an employee, which serves as the trigger for the logic bomb to execute its destructive function. Logic bombs can be particularly insidious because they may remain dormant until the triggering event occurs, making them hard to detect during normal operations.

Rootkits typically provide unauthorized access to a computer while hiding their presence. They do not specifically relate to triggering actions based on events like employee terminations. Trojan horses disguise themselves as legitimate software but often perform harmful actions without the user's knowledge, while worms are self-replicating programs that spread across networks. None of these options fit the specific scenario given in the question, emphasizing why the logic bomb is the most appropriate answer.