Abstract
As control system networks are being connected to
enterprise level networks for remote monitoring, operation, and
system-wide performance optimization, these same connections
are providing vulnerabilities that can be exploited by malicious
actors for attack, financial gain, and theft of intellectual
property. Much effort in cyber-physical system (CPS) protection
has focused on protecting the borders of the system through
traditional information security techniques. Less effort has
been applied to the protection of cyber-physical systems from
intelligent attacks launched after an attacker has defeated the
information security protections to gain access to the control
system.
In this paper, attacks on actuator signals are analyzed from
a system theoretic context. The threat surface is classified into
finite energy and bounded attacks. These two broad classes
encompass a large range of potential attacks. The effect of
theses attacks on a linear quadratic (LQ) control are analyzed,
and the optimal actuator attacks for both finite and infinite
horizon LQ control are derived, therefore the worst case attack
signals are obtained. The closed-loop system under the optimal
attack signals is given and a numerical example illustrating the
effect of an optimal bounded attack is provided.
