  Networked control systems consist of distributed sensors and actuators that
communicate via a wireless network. The use of an open wireless medium and
unattended deployment leaves these systems vulnerable to intelligent
adversaries whose goal is to disrupt the system performance. In this paper, we
study the wormhole attack on a networked control system, in which an adversary
establishes a link between two distant regions of the network by using either
high-gain antennas, as in the out-of-band wormhole, or colluding network nodes
as in the in-band wormhole. Wormholes allow the adversary to violate the timing
constraints of real-time control systems by delaying or dropping packets, and
cannot be detected using cryptographic mechanisms alone. We study the impact of
the wormhole attack on the network flows and delays and introduce a
passivity-based control-theoretic framework for modeling the wormhole attack.
We develop this framework for both the in-band and out-of-band wormhole attacks
as well as complex, hereto-unreported wormhole attacks consisting of arbitrary
combinations of in-and out-of band wormholes. We integrate existing mitigation
strategies into our framework, and analyze the throughput, delay, and stability
properties of the overall system. Through simulation study, we show that, by
selectively dropping control packets, the wormhole attack can cause
disturbances in the physical plant of a networked control system, and
demonstrate that appropriate selection of detection parameters mitigates the
disturbances due to the wormhole while satisfying the delay constraints of the
physical system.
