The department of homeland security was created to keep noncitizens from entering the united states. protect the united states from terrorist attacks. make us citizens more secure in their homes. strengthen us military presence overseas.

The department of homeland security was created to Protect the United states from terrorist attack.
To put it simply, their main duty is to prevent the act of terrorism toward united states from happening, through various surveillance and Data analysis

It is state and federali really hope this