Using technology for every threat may cost more and reduce risk less than measures such as increasing visa reviews in “high-risk” countries, said David Schanzer, director of the Triangle Center on Terrorism and Homeland Security at Duke University and the University of North Carolina.

“Every time we have an episode, we should not rush to judgment and spend billions of dollars deploying the newfangled technology that will meet a very narrow sliver of the threat,” said Schanzer. “That’s not a satisfying response that politicians can make. Politicians feel an urgent need to respond to the threats today.”