He has served as chief counterterrorism advisor to U.S. President Barack Obama; his title was Deputy National Security Advisor for Homeland Security and Counterterrorism, and Assistant to the President.^[2][3][5] His responsibilities included overseeing plans to protect the country from terrorism and respond to natural disasters, and he met with the President daily.^[6][7] Previously, he advised Obama on foreign policy and intelligence issues during the 2008 presidential campaign and transition.^[8] Brennan withdrew his name from consideration for Director of the Central Intelligence Agency (CIA) in the first Obama administration over concerns about his support for the use of torture by the CIA under President George W. Bush.^[3][6] Instead, Brennan was appointed Deputy National Security Advisor, a position which did not require Senate confirmation.^[3][6][9]

Brennan's 25 years with the CIA included work as a Near East and South Asia analyst, as station chief in Saudi Arabia, and as director of the National Counterterrorism Center.^[3][6][10] After leaving government service in 2005, Brennan became CEO of The Analysis Corporation, a security consulting business, and served as chairman of the Intelligence and National Security Alliance, an association of intelligence professionals.^[11]