Proceedings of the 2008 Winter Simulation Conference
William E. Weiss
DYNAMIC SECURITY: AN AGENT-BASED MODEL FOR AIRPORT DEFENSE
William E. Weiss
The MITRE Corporation
7515 Colshire Drive
McLean, Virginia 22102, USA
ABSTRACT
The Department of Homeland Security (DHS) shifted the
focus of airport security in 2004 to incorporate the need to
continuously and rapidly adapt security to shifting threats.
MITRE is developing a Dynamic Security Airport Simu-
lation as part of a MITRE-sponsored research project in
which attacker and defense behavior in the airport envi-
ronment are modeled. The simulation accepts threat vec-
tors (path-weapon combinations) from other software or
the user and models the performance of the airport de-
fense against those threat vectors. The simulation includes
two intelligent agents: the attacker and the defense. These
agents model the behavior of those two entities; their
logic includes both decision making and learning.
1 INTRODUCTION
The Transportation Security Administration, a branch of
the Department of Homeland Security (DHS), is respon-
sible for U.S. airport security in conjunction with airport
operators. DHS espouses a layered, adaptive security con-
cept similar to that used in cyber security (U.S. Depart-
ment of Homeland Security 2004). The objective of this
type of security is to adapt security measures in propor-
tion to changing threats. Along with outright attacks, U.S.
airport operators can expect probes from attackers, de-
signed to test their defenses. These probes supply the at-
tacker with information on the airport’s defenses, but can
also supply the airport’s defense with information on the
attacker if the probes are detected. Although these probes
occur at a much lower rate than probes of cyber security,
airport operators must still be prepared to act on informa-
tion obtained from them.
In 2004, DHS shifted the focus of airport security, in-
corporating the need to continuously and rapidly adapt se-
curity to shifting threats (Chertoff 2005). A DHS strategic
review that followed also emphasized this strategy, along
with the need for analytic tools to help match security to
perceived threats.
At this time there are few tools available to the air-
port security coordinator to test how well the airport is sa-
feguarded against changing threats. Only a very small
number of attack scenarios can feasibly be tested in live
exercises. Red Teams are somewhat less expensive and
difficult to set up than live exercises, but still cannot be
used to assess large numbers of threat scenarios.
Thus MITRE, a not-for-profit organization chartered
to work in the public interest, began to investigate airport
security risk as a function of perceived threats, measuring
how well security designs and procedures match up
against dynamic threats. One aspect of that research in-
volved assessing the threat vectors (path-weapon combi-
nations) most likely to result given at least some knowl-
edge of attacker’s goals and capabilities. The threat
vectors from that research, or threat vectors generated by
the user, feed the Dynamic Security Airport Simulation.
2 SIMULATION DESIGN
The simulation is being developed using ExtendSim Ver-
sion 7, which lends itself to agent-based simulation. Mod-
elers build simulations with ExtendSim by adding icons
(called “blocks”) to a worksheet. Each type of block has a
different function, and ExtendSim comes with many doz-
ens of blocks. Any set of blocks can be combined into a
hierarchical block, or h-block. Although many simula-
tions can be written using the included blocks, the user
can write his own code to perform specialized functions.
(This is likely to be necessary in more-complex simula-
tions, although ExtendSim supplies shortcuts to minimize
the amount of code required.) The blocks are connected to
define the network and provide pathways for both data
and the simulated items (people) to traverse. The simula-
tion is then executed. Included two-dimensional graphics
illustrate model flow and help with debugging.
The complex, adaptive system being simulated is one
of passengers progressing through an airport terminal, en
route to their departing flights, and of airport and airline
employees en route to their work areas. The model as-
sumes that some of these people are attackers; each at-
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