The U.S. federal court system was hacked Friday, with access to its public website blocked and lawyers and litigants unable to file legal documents online.The federal court's public hub, uscourts.gov, most if not all federal court sites, and the federal court system's electronic filing system were affected, a spokesman for the Administrative Office of the U.S. Courts told Politico.com.The spokesman characterized the hack as a denial-of-service attack, and said the court system would investigate as it manages its own cybersecurity service.No identification has been made of the possible source of the hacking or the people behind it, he said.Neither the Justice Department nor the Department of Homeland Security could be reached for comment on the attack, Politico said