Authorities from 21 countries took down 53 domains and arrested four people allegedly involved in distributed denial-of-service operations used by more than 75,000 cybercriminals, Europol said Thursday.  The globally coordinated effort dubbed “ Operation PowerOFF ” disrupted booter services and seized and dismantled infrastructure, including servers and databases, that supported the DDoS-for-hire services, officials said. Law enforcement agencies obtained data on more than 3 million alleged