There are machines used in telephone tapping. Is it permissible to use such devices without the knowledge of the intended personin order to use it against them when the need arises?
Answer
It is not obligatory on one speaker to ask the permission of the other speaker to record the conversation on the telephone line. However, he is not allowed to publicize it or let others listen to it if it will cause an insult of a mo’min or disclose his secret — unless that is over-ridden by another equal or more important obligation.