The United States does not have any Internet Service Provider ( ISP ) mandatory data retention laws similar to the European Data Retention Directive . Some attempts to create mandatory retention legislation have failed : It is often argued that data retention is necessary to combat terrorism , and other crimes . Data retention may assist the police and security services to identify potential terrorists and their accomplices before or after an attack has taken place . For example , the authorities in Spain and the United Kingdom stated that retained telephony data made a significant contribution to police enquires into the 2004 Madrid train bombings and the 2005 London bombings
2004 Madrid train bombings
2004 Madrid train bombings
Data retention