Complete Security From Terrorist Attacks Not Realistic

"While it would be irresponsible not to take what measures we can against the threat of terror, there is something slightly hopeless about installing security devices aimed at foiling a terrorist plot whose precise shape remains unknown. That is the quandary of fighting terror. Doing nothing risks a repeat performance; doing something merely requires terrorists to come up with different tactics. Innumerable plane hijackings in the 1970s caused airlines to progressively beef up security. When they matched bags to passengers, terrorists hid explosives in the luggage of unaware travelers. The bomb that downed Pan Am Flight 103 was camouflaged by being hidden in a radio; the 9/11 suicide terrorists didn't use explosives at all."