Friday night's attacks in Paris were a tragic reminder that with persistence and innovation, terrorists can and do strike their "enemies" at a time and place of their own choosing. It may, unfortunately, be the new normal in countries that, until recently, were thought to be immune or nearly so from such attacks.

What is most disconcerting about the Paris attacks is that while they were clearly well-planned and coordinated, they were also relatively low-tech and simple to carry out, which is the reason is why counterterrorism officials are so concerned.

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