Meet Diesel. He lives next door to me and as his owner tells it, Diesel is always a "nice" dog, but sometimes not a very "good" one. This photo is one of his latest adventures -- he managed to figure out how to open a freezer door and gorged himself on ice cream. He looks pretty happy about that, but his owners were not so pleased.
When they shared the photo with me, I had an ephiphany -- raising a dog like Diesel is just like counter-terrorism! The concientious dog owner can reduce risks of bad behavior, but short of getting rid of the dog there is no way to prevent it altogether. Dogs are adaptive adversaries; quite single-minded in their goals. And while their owners need to be successful 100% of the time, the dog needs to only find a single failure point in the defense (who would ever think of locking a freezer door?) to succeed. And, the little children in the household are always criticizing mom and dad for being too harsh on the poor dog --until after all their ice cream is gone, when mom and dad were, it seems, far too lenient.
My word -- just substitute "terrrorist" for "dog;" "DHS" for "mom and dad" or "owners;" and "the American public" for the "child" and there you have it -- a perfect expression of the counter-terrorism dilemma. Sadly, the stakes in counter-terrorism are much higher; but the principles are nearly identical.