What is the ruling of Islamic law on dealing with money left by a deceased person in an overseas bank, which has not been claimed by any of his heirs, knowing that there is an offer to transfer and divide it?

Most likely, this is a scam to obtain money or account information. Even if there were real funds belonging to a deceased person, it is impermissible to take them unjustly or to assist bank employees in a trick to withdraw them, for Allah Almighty says: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression. And fear Allah; indeed, Allah is severe in penalty."