5 different levels starting from severe to moderate of threats
The Department of Homeland Security has a vital mission: to secure the nation from the many threats we face. This requires the dedication of more than 240,000 employees in jobs that range from aviation and border security to emergency response, from cybersecurity analyst to chemical facility inspector. Their duties are wide ranging, and their goal is clear - keeping America safe. The Department of Homeland Security combined 22 different federal departments and agencies into a unified, integrated cabinet agency when it was established in 2002. Eleven days after the September 11, 2001, terrorist attacks, Pennsylvania Governor Tom Ridge was appointed as the first Director of the Office of Homeland Security in the White House. The office oversaw and coordinated a comprehensive national strategy to safeguard the country against terrorism and respond to any future attacks.
With the passage of the Homeland Security Act by Congress in November 2002, the Department of Homeland Security formally came into being as a stand-alone, Cabinet-level department to further coordinate and unify national homeland security efforts, opening its doors on March 1, 2003.