The source are talk and wish dreams and nothing more.

Elon said a anti missile shield called SHIELD would be cool (nooo, Elon had another random idea from someone who doesn't know the field but has enough pr clout to make it published?), and Elon used to work or at least be in the same building as a general when he visits for a company that do space launch and is critical to US infrastructure needs (noo? you don't say ?) , and someone else said about shield against missile wouldn't be cool (noo?). That's nothing real or factual.