Two weeks ago in Boston, authorities stopped a disturbed young man before he could launch a terror attack; tragically, last week in Chattanooga, the story ended very differently. Law enforcement officials are scrambling to learn whether clues were missed that could have prevented the rampage and led to the alleged shooter, Mohammod Youssuf Abdulazeez. But in too many cases, the breadcrumb trail starts with suspicious ones and zeros — with digital propaganda that we still struggle to counter.

In 2007, when Twitter was a year young and WhatsApp was still two years away, I introduced a bill that would have set up a national commission to study the new ways that terror groups were reaching the lost, disaffected and psychopathic. The Violent Radicalization and Homegrown Terrorism Prevention Act of 2007 passed the House of Representatives by a vote of 404 to 6, before it was misconstrued by outside groups and mothballed by the Senate.

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