The Department of Homeland Security performs a number of different functions. They have a department that specializes in counter terrorism, meaning that they protect the United States against terrorist attacks by trying to find out about these attacks (both physical and chemical weapons) before they happen and stopping them from happening in the first place. They do this by protecting airports and waterways as well as other thoroughfares and by sharing information with other intelligence agencies as needed. Homeland Security also maintains border security, keeping US borders safe, handles immigration issues, and is actively involved in both disaster preparedness and disaster response efforts. Essentially, all of the things that we need to keep us safe and sound are, in some way, touched on by Homeland Security. For more information, you can visit their web page included below. There is also a lot of helpful information that they compile such as what passengers can take on airplanes and how to keep yourself safe while traveling.
The Department of Homeland Security deals with numerous kinds of threats that could occur on Unites States soil. They focus on current and future attacks that may occur. Just a few of the issues they look at as far as possible threats are concerned are transportation systems, nuclear threats, and biological threats.
Their goal is to reduce risk to any threats that may occur in the United States and protect human life. In addition, they work in research and development, training, and long term protection of the United States. They also work with several other agencies such as Border Protection that deals with illegal immigration, the Secret Service which protects the President, the Coast Guard and FEMA just to name a few.
When most people think of Homeland Security, they think of the people trying to stop terrorists from getting on airplanes. Homeland Security does do that, but they are also involved in a lot of other functions.
For example, Homeland Security is the parent agency of FEMA, the emergency management people who were in charge of the response to Hurricane Katrina.
In addition, Homeland Security is in charge of the ICE -- the immigration people who are supposed to be in charge of enforcing immigration law.
Homeland Security is even responsible for the agents who check agricultural products coming into the country.
One of their original functions was to act as a sort of clearing house for information from all the intelligence and security organizations in the Unites States. It was a well known fact, and a much more widely known fact after 9/11, that the various intelligence agencies such as the CIA and the FBI and the NSA did not communicate very well and often held on to good intelligence desperately as the whole thing was seen as a sort of turf war. In order to improve the function of those agencies and our ability to respond to or avert terrorist threats, the Department of Homeland Security was tasked with finding a way to help these agencies communicate through improved technological connection as well as interagency meetings and cooperative efforts.
Some would argue that this has been largely unsuccessful given our recent experience with the attempted bombing of the flight landing at Detroit and the fact that the State Department had not been able to communicate with the various agencies that might have been able to stop him from boarding the plane in the first place.