What is the ruling on automatically recording calls without the knowledge of the parties involved?

It is not permissible to record voice calls without the owner's permission, unless their consent is known. Otherwise, it involves transgression and betrayal. If the recording is broadcasted and contains content that spoils relationships, this falls under forbidden backbiting (namimah (definition)). The Messenger of Allah, peace and blessings be upon him, said: "If a man narrates a حديث (statement/story) and then turns around, it is a trust," and "Gatherings are by trust." Therefore, it is part of the trust not to record a call from someone who dislikes it or does not permit it, especially if the recording harms Muslims or exposes their faults, based on the Prophet's saying, peace and blessings be upon him: "Do not harm Muslims, nor humiliate them, nor pursue their faults," and "There shall be no harm or reciprocating of harm." If it is known that the caller does not dislike this, then there is no harm. Otherwise, one must ask and seek their permission, except in cases of legitimate espionage.