Malicious self-replicating codes, known as malware, pose substantial threat to wireless networks, and the economic viability of the investments directed towards wireless infrastructure is contingent on the design of effective countermeasures. The first step towards this end is to anticipate malware hazards, and understand the threat before the attacks are actually launched. In this talk, we quantify the fundamental limits on the damage that the malware can inflict by optimally choosing its actions. Such limitations arise because the capabilities of the malware are limited by the resource constraints x of wireless networks which the malware utilizes as well to propagate the contagion. Specifically, malware needs to decide how best to utilize the limited battery reserves of the host in scanning the media and transmitting packets that carry the contagion, as once the host's battery is depleted, the network incurs a cost, but so does the malware as the host can no longer be utilized to propagate the contagion and also in fulfilling its subversive ends. We formulate the maximization of the overall damage inflicted on the network as an optimal control problem, and subsequently identify structural properties of the optimal actions of the malware using Pontryagin's Maximum Principle. We show that the malware can inflict the maximum damage by choosing simple bang-bang control functions with at most two jumps. The network can launch counter-measures through power control based quarantining strategies and also by fetching security patches that immunize the vulnerable and heal the infected hosts. Such power control strategies however deteriorate the quality of service in the network, and the transmission of patches consume valuable transmission resources such as spectrum and energy. We formulate the optimal countermeasure selection as optimal control problems and identify structural properties of the optimal solutions. The optimal strategies again turn out to be bang-bang functions with at most two jumps, and should therefore be readily implementable in resource constrained wireless devices.
Saswati Sarkar received her BS from Jadavpur University in 1994, MS from Indian Institute of Science Bangalore in 1996 and PhD in 2000 from the Electrical and Computer Engineering Department in University of Maryland, College Park. She is currently an associate professor in the Electrical and Systems Engineering department at the University of Pennsylvania, where she joined as an assistant professor in 2000. She received the Motorola gold medal for being adjudged the best masters student in the division of electrical sciences at the Indian Institute of Science, Bangalore, and also received the NSF career award in 2003. Her research interests are in resource allocations, security and economics of wireless networks. She has served as an associate editor in IEEE Transactions in Wireless Networks from 2001 to 2006, and is currently on the editorial board of IEEE/ACM Transactions on Networking.