Audit all visa's for expiration and start deporting them.
9/11 hijackers were on expired visas.
Boston Marathon Bombers came via visa, asylum, and chain migration. They travelled to Dagestan/Chechnya, were more radicalized, were allowed to return, and launched a terrorist attack.
Asylum seekers shoud be vetted while still outside the United States. Those that come on a visa, and later request asylum, should be required to leave the United States to apply for asylum.
Visas and Asylum should be denied to those traveling from areas that are hotbeds for radicalism and terrorism.