A ransomware attack targeting the huge Los Angeles school district prompted an unprecedented shutdown of its computer systems as schools increasingly find themselves vulnerable to cyber breaches at the start of a new year.

The attack on the Los Angeles Unified School District sounded alarms across the country, from urgent talks with the White House and the National Security Council after the first signs of ransomware were discovered late Saturday night to mandated password changes for 540,000 students and 70,000 district employees.