Dark Networks

Vladis Krebs has a case study
page examining how mapping social networks and understanding their
properties can be used to take down of terrorist networks. Network analysis was used to take
down Saddam Hussein. The

Washington Post has some of the details.

The Army general whose forces captured Saddam Hussein said yesterday that
he realized as far back as July that the key lay in figuring out the former
Iraqi president's clan and family support structures in and around Hussein's
home city of Tikrit.

Following a strategy similar to that pioneered by New York City police in
the 1990s, who cracked down on "squeegee men" only to discover they knew about
far more serious criminals, Maj. Gen. Raymond T. Odierno said his analysts and
commanders spent the summer building "link diagrams," graphics showing
everyone related to Hussein by blood or tribe.

While U.S. forces up to then had been preoccupied with finding "high value
targets" from the Bush administration's list of the top 55 most-wanted Iraqis,
Odierno said those family diagrams led his forces to lower-level, but
nonetheless highly trusted, relatives and clan members harboring Hussein and
helping him move around the countryside.

And the rest as they say, is history.
John Robb took at look at the September 11 network and analyzed its
characteristics. The Mohammed Atta network had evolved under Darwinian pressure
until it reached the form best suited for its purpose: to conduct strategic
attacks against the United States of America. Robb concludes that a cell of 70
persons will answer to the purpose, yet be sparse enough to allow its
members to remain in relative isolation. For example, no one member of Atta's
cell knew more than five others. Moreover, the average distance between any two
members was more than four persons. Crucially, but not surprisingly, this
disconnected network of plotters maintained coherence by relying on a support
infrastructure -- probably communications posts, safe houses, couriers -- to
keep themselves from unraveling.  Because security comes at a price in
performance and flexibility, Robb arrives at an

astounding conjecture: you can have small, operationally secure terrorist
groups, but you can't have large, operationally secure cells without a state
sponsor.

Distributed, dynamic terrorist networks cannot scale like hierarchical
networks. The same network design that makes them resiliant against attack
puts absolute limits on their size. If so, what are those limits?

A good starting point is to look at limits to group size within peaceful
online communities on which we have extensive data -- terrorist networks are
essentially geographically dispersed online communities. Chris Allen does a
good job analyzing optimal group size with his critique of the Dunbar
number.

His analysis (replete with examples) shows that there is a gradual fall-off
in effectiveness at 80 members, with an absolute fall-off at 150 members. The
initial fall-off occurs, according to Chris, due to an increasing amount of
effort spent on "grooming" the group to maintain cohesion. The absolute
fall-off at 150 members occurs when grooming fails to stem dissatisfaction and
dissension, which causes the group to cleave apart into smaller subgroups
(that may remain affiliated).

Al Qaeda may have been able to grow much larger than this when it ran
physical training camps in Afghanistan. Physical proximity allowed al Qaeda to
operate as a hierarchy along military lines, complete with middle management
(or at least a mix of a hierarchy in Afghanistan and a distributed network
outside of Afghanistan). Once those camps were broken apart, the factors
listed above were likely to have caused the fragmentation we see today (lots
of references to this in the news).

His last paragraph is crucial to understanding why the defeat of the Taliban
in Afghanistan and the toppling of Saddam Hussein may have cripped global
terrorism so badly. Without the infrastrastructure of a state sponsor, terrorism
is limited to cells of about 100 members in size in order to maintain security.
In the context of the current campaign in Iraq, the strategic importance of
places like Falluja or "holy places" is that their enclave nature allows
terrorists to grow out their networks to a larger and more potent size. Without
those sanctuaries, they would be small, clandestine hunted bands. The

argument that dismantling terrorist enclaves makes "America less safe than
it should be in a dangerous world" inverts the logic. It is allowing the growth
of terrorist enclaves that puts everyone at risk in an otherwise safe world.

Update

Here's a link to a database of terrorist incidents called,
MIPT Terrorism, via
the Neophyte Pundit.
I'll look into the site later today or this week, but it seems useful enough to
put on my blogroll.