What is the remit of the U.S.'s Dept of Homeland Security? How does it relate to the Department of Justice and its agencies, FBI and ATF (and others?)? What is

What is the remit of the U.S.'s Dept of Homeland Security? How does it relate to the Department of Justice and its agencies, FBI and ATF (and others?)? What is the oversight and limit on DHS's power? Remember that DHS is much more than immigration. It contains FEMA, the Secret Service, TSA, the Coast Guard, and more. If I understand correctly, DHS's focus was supposed to be terrorism and, apparently, border security. However, as I've posted before, it seems to claim a broader jurisdiction:[0] As the investigative arm of the Department of Homeland Security, ICE is responsible for the enforcement of laws that promote the legitimate movement of people, goods and currency in domestic and foreign transactions. That quote is related to DHS taking down a website involved in prostitution. In the OP, DHS is involved in data breaches. Neither of those actions seem related to terrorism or border security. The quoted definition is very broad; it includes almost everything that every business or individual does. It's the nature of bureaucracies to try to expand their power, but I wonder how this overlaps or competes with the Department of Justice, if DHS has the same legal oversight as DOJ, and if it's political - DHS seems more willing to carry out the President's policy than DOJ, which has an obligation to remain independent. [0] https://www.nytimes.com/2015/08/27/nyregion/raid-of-rentboy-an-escort-website-angers-gay-activists.html https://www.nytimes.com/2015/08/27/nyregion/raid-of-rentboy-...