By Francesco Guarascio BRUSSELS (Reuters) – The European Union is considering testing banks' defenses against cyber attacks, EU officials and sources said, as concerns grow about the industry's vulnerability to hacking. Cyber attacks against banks have increased in numbers and sophistication in recent years, with criminals finding new ways to target banks beyond trying to illicitly obtain details of their customers' online accounts. Global regulators have tightened security requirements for banks after that giant cyber fraud, one of the biggest in history, and in some countries have carried out checks on lenders' security systems.