447 research outputs found
Information Flow for Security in Control Systems
This paper considers the development of information flow analyses to support
resilient design and active detection of adversaries in cyber physical systems
(CPS). The area of CPS security, though well studied, suffers from
fragmentation. In this paper, we consider control systems as an abstraction of
CPS. Here, we extend the notion of information flow analysis, a well
established set of methods developed in software security, to obtain a unified
framework that captures and extends system theoretic results in control system
security. In particular, we propose the Kullback Liebler (KL) divergence as a
causal measure of information flow, which quantifies the effect of adversarial
inputs on sensor outputs. We show that the proposed measure characterizes the
resilience of control systems to specific attack strategies by relating the KL
divergence to optimal detection techniques. We then relate information flows to
stealthy attack scenarios where an adversary can bypass detection. Finally,
this article examines active detection mechanisms where a defender
intelligently manipulates control inputs or the system itself in order to
elicit information flows from an attacker's malicious behavior. In all previous
cases, we demonstrate an ability to investigate and extend existing results by
utilizing the proposed information flow analyses
On Reachable Sets of Hidden CPS Sensor Attacks
For given system dynamics, observer structure, and observer-based
fault/attack detection procedure, we provide mathematical tools -- in terms of
Linear Matrix Inequalities (LMIs) -- for computing outer ellipsoidal bounds on
the set of estimation errors that attacks can induce while maintaining the
alarm rate of the detector equal to its attack-free false alarm rate. We refer
to these sets to as hidden reachable sets. The obtained ellipsoidal bounds on
hidden reachable sets quantify the attacker's potential impact when it is
constrained to stay hidden from the detector. We provide tools for minimizing
the volume of these ellipsoidal bounds (minimizing thus the reachable sets) by
redesigning the observer gains. Simulation results are presented to illustrate
the performance of our tools
A Comparison of Stealthy Sensor Attacks on Control Systems
As more attention is paid to security in the context of control systems and
as attacks occur to real control systems throughout the world, it has become
clear that some of the most nefarious attacks are those that evade detection.
The term stealthy has come to encompass a variety of techniques that attackers
can employ to avoid detection. Here we show how the states of the system (in
particular, the reachable set corresponding to the attack) can be manipulated
under two important types of stealthy attacks. We employ the chi-squared fault
detection method and demonstrate how this imposes a constraint on the attack
sequence either to generate no alarms (zero-alarm attack) or to generate alarms
at a rate indistinguishable from normal operation (hidden attack)
Distributed watermarking for secure control of microgrids under replay attacks
The problem of replay attacks in the communication network between
Distributed Generation Units (DGUs) of a DC microgrid is examined. The DGUs are
regulated through a hierarchical control architecture, and are networked to
achieve secondary control objectives. Following analysis of the detectability
of replay attacks by a distributed monitoring scheme previously proposed, the
need for a watermarking signal is identified. Hence, conditions are given on
the watermark in order to guarantee detection of replay attacks, and such a
signal is designed. Simulations are then presented to demonstrate the
effectiveness of the technique
- …