Al Qaeda is so weak that they have to depend upon Western technology. They ride Western trains, rent Western cars, use Western phones, internet, mail, etc.
In earlier times, they would have depended upon Chairman Mao's defense of "swimming with the fish in the sea" to avoid detection. That's not such a safe option any longer.
The closest that Al Qaeda has to its own "infrastructure" is its system of moving small cash payments through trusted intermediaries...outside of that, some radical mosques, and the madrassas, they have no infrastructure that they can call their own. They must depend upon their enemies' infrastructures then, a fundamental (pun intended) strategic weakness.
This is not to say that they can't inflict pain, but it does show that they can *not* by definition possess the resources to overwhelm the West.
Which is to say that they've picked a very foolish fight.