Well, DUH! Yes…depending on where they are coming from, and ALWAYS if they are Muslims or coming from Muslim countries.
The U.S. government may impose tighter scrutiny of visa-seekers’ social media accounts following revelations that one of the San Bernardino attackers discussed violence before she was allowed into the country.(Nothing like shutting the barn door after the camel is gone. How about checking the social media of all the Muslims who have already gotten in on visas?)