The Storm botnet is one of the most sophisticated botnet active today, used for a variety of illicit activities. A key requirement for these activities is the ability by the botnet operators to transmit commands to the bots, or at least to the various segmented portions of the botnet. Disrupting these command and control (C&C) channels therefore becomes an attractive avenue to reducing botnets effectiveness and efficiency. Since the command and control infrastructure of Storm is based on peer-to-peer (P2P) networks, previous work has explored the use of index poisoning, a disruption method developed for file-sharing P2P networks, where the network is inundated with false information about the location of files. In contrast, in this paper we explore the feasibility of Sybil attacks as a mitigation strategy against Storm. The aim here is to infiltrate the botnet with large number of fake nodes (sybils), that seek to disrupt the communication between the bots by inserting themselves in the peer lists of “regular” bots, and eventually re-reroute or disrupt “real” C&C traffic. An important difference with index poisoning attacks is that sybil nodes must remain active and participate in the underlying P2P protocols, in order to remain in the peer list of regular bot nodes. However, they do not have to respond to the botmaster’s commands and participate into illicit activities. First, we outline a methodology for mounting practical Sybil attacks on the Storm botnet. Then, we describe our simulation studies, which provide some insights regarding the number of sybils necessary to achieve the desired level of disruption, with respect to the net growth rate of the botnet. We also explore how certain parameters such as the duration of the Sybil attack, and botnet design choices such as the size of a bot’s peer list, affect the effectiveness of the attack.
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