T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering 1 Xun Wang †, Sriram Chellappan †, Wenjun Gu †, Wei Yu ‡ and Dong Xuan † Presented by Xun Wang † Department of Computer Science and Engineering The Ohio State University ‡ Department of Computer Science Texas A & M University Xun Wang †, Sriram Chellappan †, Wenjun Gu †, Wei Yu ‡ and Dong Xuan † Presented by Xun Wang † Department of Computer Science and Engineering The Ohio State University ‡ Department of Computer Science Texas A & M University Search-based Physical Attacks in Sensor Networks

T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering 2 Physical Attacks are Salient Threats to Sensor Networks Sensor network applications that operate in hostile environments –Volcanic monitoring –Battlefield applications –Anti sensor network forces Physical attacks are inevitable in sensor networks –Physical attacks: destroy sensors physically –Simple to launch Small form factor of sensors Unattended and distributed nature of deployment –Can be fatal to sensor networks –Different from other types of electronic attacks We study impacts of different types of physical attacks and the countermeasures.

T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering 3 Outline Physical Attacks in sensor networks Modeling Search-based physical attacks Performance evaluations Countermeasures to Physical Attacks Final remarks

T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering 4 Physical Attacks – A General Description Two phases –Targeting phase –Destruction phase Two broad types of physical attacks –Blind physical attacks –Search-based physical attacks

T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering 5 Blind Physical Attacks Targeting phase –Identifying the sensor network deployment field Destruction phase –Randomly/ blindly selecting attack area –Brute-force physical destruction with bombs/grenades or tanks/vehicles –Sensors in the attack area are destroyed Features –Fast –Not accurate due to blind destruction –Larger causalities to deployment field Xun Wang, W. Gu, S. Chellappan, K. Schosek and D. Xuan, Lifetime Optimization of Sensor Networks under Physical Attacks, IEEE International Conference on Communications (ICC), 2005 Lifetime Optimization of Sensor Networks under Physical Attacks

T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering 6 Search-Based Physical Attacks Targeting phase –Searching for sensors by detecting signals emitted by sensors (heat, magnetic and electronic signals) –Isolating an area for each detected sensor Destruction phase –Reaching the isolation area of each detected sensor –Destroying small size sensors through physical destruction methods (like physical force, radiation, hardware/circuit tampering)--sweeping Features –Slow –Accurate destruction of only isolated area –Better preserves the deployment field (airports, oil fields, battlefield). It can be an important agenda for the attacker. In extreme cases, the enemy of the attacker can deploy sensor networks in the attacker’s land and the attacker needs to remove the sensors while preserving the land.

T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering 7 Modeling of Search-based Physical Attacks Sensor network signals –Passive signal and active signal –Signals and roles in hierarchical sensor networks (normal sensors and cluster-heads) Attacker capacities –Signal detection and sensor Isolation –Attacker movement –Sensor destruction method Attack Model –Attacker objective –Attack procedure and scheduling

T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering 8 Network Parameters and Attacker Capacities f: Active signal frequency μ: Cluster-head rotation frequency C: Cluster size R ps : The maximum distance can detect a passive signal R as s : The maximum distance can detect an active signal emitted by a normal sensor R as h : The maximum distance can detect an active signal emitted by a cluster-head θ: Isolation accuracy –r i =d i θ –Isolation/sweeping area: Bi=πr i 2 V mv : Attacker moving speed V sw : Attacker sweeping speed

T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering 9 Attacker objective and attack procedure AC: Accumulative Coverage –EL: Effectively Lifetime is the time period until when the sensor network becomes nonfunctional because the coverage falls below a certain threshold α –Coverage(t): Instant network coverage at time t Objective: Decrease AC.

T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering 10 Attacker Activity Scheduling Scheduling of the movement when there are multiple detected sensors –In our model, the attacker chooses the one that it needs to spend least time to reach and destroy (finish the sweeping of isolation area) –Optimal scheduling? –Due the dynamics of the attack process, it is hard to get the optimal path in advance Tradeoff between attacking normal sensors first and cluster-heads first –Attacking cluster-heads causes larger damage to coverage but might take longer time –Weighted selection: combine the time cost and the weight of detected sensors –PA/H (larger weights for cluster-heads) v.s. PA/NH (same weights)

T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering 11 Sensitivity to Attacker Capacities

T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering 12 Sensitivity to Sensor Network Parameters

T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering 13 Sensitivity to Sensor Network Parameters

T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering 14 Countermeasures to Physical Attacks For Blind physical attacks –Optimally over-deploying sensors to prolong lifetime of sensor networks under blind physical attacks For Search-based physical attacks –Deterring the search process (at the target phase) ┼Physically protecting sensors

T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering 15 Defending Sensor Networks against Search-based Physical Attacks Adopting Sacrificial Nodes (sensors) to improve monitoring of the attacker and to increase the protection areas provided by Attack Notifications. –A sacrificial node is one that detects the attacker in order to protect other sensors at the risk of itself being detected and destroyed by the attacker. –Attack Notifications from victim sensors. –States Switching of receiver sensors of Attack Notifications to reduce the number of detected sensors. –Trade short term local coverage for long term global coverage. W. Gu, Xun Wang, S. Chellappan, D. Xuan and T. H. Lai, Defending against Search-based Physical Attacks in Sensor Networks, accepted by IEEE Mobile Sensor and Ad-hoc and Sensor Systems (MASS) 2005.Defending against Search-based Physical Attacks in Sensor Networks

T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering 16 Final Remarks Physical attacks are patent and potent threats to sensor networks. We modeled Search-based Physical attack and analyzed its impacts to sensor networks in this paper. Viability of future sensor networks is contingent on their ability to defend against physical attacks.

T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering T H E O H I O S T A T E U N I V E R S I T Y Computer Science and Engineering 17 Q&A Thank You !