Keith Brian Alexander (born December 2, 1951) is a retired four-star general of the United States Army, who served as director of the National Security Agency, chief of the Central Security Service, and commander of the United States Cyber Command. He previously served as Deputy Chief of Staff, G-2 (Intelligence), United States Army from 2003 to 2005. He assumed the positions of Director of the National Security Agency and Chief of the Central Security Service on August 1, 2005, and the additional duties as Commander United States Cyber Command on May 21, 2010.