(Presidential Decision Directive-63) An order by President Clinton on May 22, 1998 to define U.S. federal government policies on critical infrastructure protection. PDD-63 is the foundation document for the creation of the National Infrastructure Protection Center (NIPC), the United States Computer Emergency Readiness Team (US-CERT) and other organizations devoted to protecting the nation's crucial industrial and financial base. For more information, visit www.fas.org/irp/offdocs/pdd/pdd-63.htm. See critical infrastructure.