An orange box is a piece of hardware or software that emulates caller ID FSK signals to spoof caller ID information on the target's caller ID terminal. It takes advantage of call waiting caller ID (also called off-hook caller ID) by mimicking the phone company's central office equipment and sending the call waiting tone followed by the audible caller ID data. An orange box can also be used to spoof the initial Caller ID information sent after an incoming call rings, if the user has direct access to the target's phone line. One proposal to accomplish this involves an orange box used in conjunction with a magenta box, which in combination is called a vermilion box.
Alternatively, in software engineering an orange box is any mechanism that records the sequence of events leading to a crash, probably by analogy to the flight data recorder (FDR) in airplanes, which is typically housed in an orange box (to ensure visibility in the wreckage after a crash). Curiously, the FDR itself is popularly (if misleadingly) known as a "black box"; possibly the term "orange box" was adopted in software engineering because "black box" already had a different meaning (see black box testing).