U.S. Secretary of Homeland Security
The Secretary of Homeland Security leads the third largest Department of the U.S. government. Kirstjen Nielsen was sworn in on December 6, 2017 as the sixth Secretary of Homeland Security. She previously served as White House Deputy Chief of Staff. Under the Secretary's leadership, DHS is responsible for counterterrorism, cybersecurity, aviation security, border security, port security, maritime security, administration and enforcement of our immigration laws, protection of our national leaders, protection of critical infrastructure, cybersecurity, detection of and protection against chemical, biological and nuclear threats to the homeland, and response to disasters.