What is the ruling on money earned from savings accounts with a fixed annual interest rate? Is it unlawful (haram)? And what should I do with the interest I have received if it is indeed unlawful?

Dealing with traditional banks for a known and guaranteed interest is a forbidden usurious transaction. And whoever has dealt with a usurious savings account while knowing its ruling, it is not permissible for him to benefit from its interest, and he must dispose of it in charitable causes. If he does not know its amount, he must strive to determine his principal to dispose of the usurious excess. As for whoever dealt with this account while not knowing its ruling, he is not obliged to dispose of its interest until after he knows the ruling.