When we look around the universe, we can see that some kind of substance is exerting enough gravity to pull on stars and galaxies and passing light, but no telescope or device has ever directly picked up the source -- hence the name 'dark matter.'
Pincho says... There's no such thing as a pull force, mass is not attracted to mass, mass moves towards holes. Holes in mass have 100% association with mass. Black holes can just be holes without mass. You don't need the mass.