Computers using AI and algorithms do the initial screening then flag any "hot" convos for humans to consider.
There is nothing "conspiracy theory" about this. It has been widely admitted by both American and Canadian governments and is operated under the guise of national security.
The Bush administration came under the gun many years ago doing this covertly.
Did you see the article online the other day that showed a CIA tracking device that was found by a Middle Eastern man who lives in the U.S? This kind of tracking has been going on as well for some time.