  A model for terrorism is presented using the theory of percolation. Terrorism
power is related to the spontaneous formation of random backbones of people who
are sympathetic to terrorism but without being directly involved in it. They
just don't oppose in case they could. In the past such friendly-to-terrorism
backbones have been always existing but were of finite size and localized to a
given geographical area. The September 11 terrorist attack on the US has
revealed for the first time the existence of a world wide spread extension. It
is argued to have result from a sudden world percolation of otherwise
unconnected and dormant world spread backbones of passive supporters. The
associated strategic question is then to determine if collecting ground
information could have predict and thus avoid such a transition. Our results
show the answer is no, voiding the major criticism against intelligence
services. To conclude the impact of military action is discussed.
