Please tell me how to screen them to remove those who may be dangerous.
Simple. By excluding the superset, you exclude all the subsets. Do not, under any circumstances, let Saudis, Yemenis, Syrians, Palestinians, Egyptians, Iranians, etc. into this country. Period.
Jordanians, Lebanese, Iraqis ... may be allowed entry, but only under tight supervision. Violation of any of the regulations and they are expelled immediately and permanently. Get a parking ticket and you're on your way home, Abdul.
We owe these animals nothing.
"Please tell me how to screen them to remove those who may be dangerous."
Block every one of them.