Tesco Bank publicized that modest amounts of funds had been stolen from 20,000 accounts this past weekend, with an additional 20,000 accounts being attacked by suspicious probes; the company manages nearly eight million accounts and they have been blocked from using debit cards since this weekend; Tesco's CEO says that they are confident they know the nature of the attack, but declined to explain at this time, and is asking UK regulators to allow them to make debit transactions allowable again as soon as possible; the UK's Financial Conduct Authority has called the attack "unprecedented in size and sophistication" but acknowledges limited IT expertise within the authority. Source