https://www.dhs.gov/operational-and-support-components list the 22 agencies of homeland security. Here are just a few
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United States Citizenship and Immigration Services.
U.S. Customs and Border Protection.
Federal Emergency Management Agency.
U.S. Immigration and Customs Enforcement.
Transportation Security Administration.
United States Coast Guard (during times of peace)
Cybersecurity and Infrastructure Security Agency
https://www.usajobs.gov/Search/Results?l=&d=HS currently lists 1096 jobs for Homeland Security