The article discusses the matter of contemporary cyberattack techniques aimed at the financial security of banks and their clients and presents the relationship of banks with their clients in the light of the applicable provisions of the European Union (Directive of the European Parliament and the EU Council 2015/2366 of November 25, 2015 on payment services in internal market) and the Polish Act of 19 August 2011 on payment services. The authors also analyze the practical side of the relationship between banks and their customers who have fallen victim to computer fraud, pointing out that the common practice of banks refusing to return funds stolen from their customers in the electronic banking system is inconsistent with the applicable standards of Polish and European law.