Here's an informative essay that is worth a look on this day. Michael Shermer recently outlined five popular misconceptions about terrorism for Scientific American magazine.
The misconceptions are these:
1. terrorists are motivated by pure evil
2. terrorists are part of a vast global network waging a centrally organised war on societies they hate
3. terrorists are disciplined, brilliant and cunning
4. terrorists are exceptionally deadly to others
5. terrorism works
Not so on all five counts, says Shermer--badly as terrorists themselves may believe some of these things and want the rest of the world to do the same.
Here's that link again. Those interested more generally in the ongoing, noble work of mythbusting will find much to explore at Michael Schermer's home page and in the magazine he founded, Skeptic.