What is the ruling on profiting from selling old Facebook accounts that have been taken over, and what is the ruling on the money earned from them and the accounts currently available whose owners are unknown?

It is not permissible to hack old Facebook accounts and sell them, as this constitutes an aggression against their owners. Even if the owners have abandoned them, these accounts belong to the website owner and are not abandoned property. The money earned from such a sale is unlawful (haram) because it is selling something you do not own. The sale must be canceled, the accounts returned to their owners, and repentance sought. If returning them is not possible, the unlawful money must be disposed of, and absolution sought from the account owners. For accounts whose owners are unknown, either contact Facebook administration to restore them, or close them so they revert to the owner. Allah Almighty says: ﴿O you who have believed, do not consume one another’s wealth unjustly but only [in lawful] business by mutual consent.﴾ And the Prophet, peace and blessings be upon him, said: "Indeed, your blood, your wealth, and your honor are sacred among you." He also said: "The wealth of a person is not lawful unless given with a willing soul." Aggression is forbidden against Muslims and non-Muslims alike, except in the case of a combatant.