Is the interest paid by banks permissible or forbidden, and does it fall under the category of usury, given that the bank's investment activities are unknown?

It is forbidden to deal with usurious banks except in cases of necessity, based on the Almighty's saying: (O you who have believed, fear Allah and give up what remains [due to you] of interest, if you should be believers. And if you do not, then be informed of a war [against you] from Allah and His Messenger). What is yielded from these funds is called forbidden usury. The Prophet, peace and blessings be upon him, said: "A dirham of usury that a man consumes knowingly is worse than thirty-six acts of fornication." As for Islamic banks that invest money according to Sharia, there is no harm in dealing with them, and the profit generated from them is lawful. The investor must verify the legitimacy of the dealings of the entity in which he invests his money.