A ransomware attack is the cause of a disruption at Marks & Spencer Group Plc., with hackers using a potent kind of malware to lock down some of the British retailer’s systems and render them inaccessible, according to people familiar …

A ransomware attack is the cause of a disruption at Marks & Spencer Group Plc., with hackers using a potent kind of malware to lock down some of the British retailer’s systems and render them inaccessible, according to people familiar …