This policy analysis identifies 154 foreign-born terrorists in the United States who killed 3,024 people in attacks from 1975 through the end of 2015. Ten of them were illegal immigrants, 54 were lawful permanent residents (LPR), 19 were students, 1 entered on a K-1 fiancé(e) visa, 20 were refugees, 4 were asylum seekers, 34 were tourists on various visas, and 3 were from Visa Waiver Program (VWP) countries. The visas for 9 terrorists could not be determined. During that period, the chance of an American being murdered by a foreign-born terrorist was 1 in 3,609,709 a year. The chance of an American being killed in a terrorist attack committed by a refugee was 1 in 3.64 billion a year. The annual chance of being murdered by somebody other than a foreign-born terrorist was 252.9 times greater than the chance of dying in a terrorist attack committed by a foreign-born terrorist.
–Alex Nowrasteh, Terrorism and Immigration: A Risk Analysis