9/11 introduced us to foreign terrorists who operated like a wolf pack.  Ten years later, the terror threat increasingly seems to come from the lone wolf.

FOX News Radio's Mike Majchrowitz explores how the nature of the threat has changed in Part 20 of our month-long special series, "9/11: 10 Years Later":

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In our next report, the challenge of building a permanent memorial to the victims of Flight 93 in Shanksville, Pennsylvania.

CLICK HERE to listen to Parts 1-19 of our month-long special series, "9/11: 10 Years Later"