The same way we find out about anything. Companies like Reuters and CNN tell us while the CIA is still snoozing.
It is entirely clear that Libertarianism does support those things and one of the two roles of a Libertarian government is the physical security of the nation and its citizens.
OK, I'll grant you the existence of the media reporting from foreign countries (although I fail to see how the "What's Xia up to" branch of Reuters makes any money).
Now, a worthy chap sees a report about Xia on CNN and gets suspicious. How's he going to get enough money to mount a publicity campaign warning Libland citizens of the danger?
It is entirely clear that Libertarianism does support those things and one of the two roles of a Libertarian government is the physical security of the nation and its citizens.