[RickFLM4]

There is no way to screen most of them, period. Doesn't matter if you have 6 mos. or 1 week to do background checks. There is either no data on many of them or no way to know who they really are. So you either take them in with a best effort on filtering out known terrorists and live with the resulting risk or you do your best to keep them out (easier in North America than Europe). There is no good answer to the problem. The entire world is completely unprepared, the result of poor strategy and a complete lack of planning. So here we are.