out-of-band

Relating to activity outside of a defined telecommunications frequency band.

In this additional spectrum, in-band signaling was sent down the wires outside the frequencies used for conversation. Actually, the signals were sent across the 3,500- and 3,700-Hz frequencies. Although these worked and were not in the talk path (out of the band) they were limited in the number of tones that could be sent.

Relating to communication on a different channel, or by a different method, from that of the primary communication channel.

Relating to communication, such as identity verification, via a method other than the primary means of accessing the software.

One great way of solving the phishing problem is doing out-of-band authentication.

Defaulting to chaos still causes a lot of disruption, and would require out-of-band social coordination to resolve, but it places a much larger barrier in front of the attacker, and makes attackers much less confident that they will be able to get away with a clean victory, making them much less motivated to even try to start an attack.

Referring to a value returned by a function that is not in its natural range of return values, but rather signals an exception.