JACKSTRAWS: Picking Command and Control Connections from Bot Traffic

A distinguishing characteristic of bots is their ability to establish a command and control (C&C) channel. The typical approach to build detection models for C&C traffic and to identify C&C endpoints (IP addresses and domains of C&C servers) is to execute a bot in a controlled environment and monitor its outgoing network connections. Using the bot traffic, one can then craft signatures that match C&C connections or blacklist the IP addresses or domains that the packets are sent to. Unfortunately, this process is not as easy as it seems. For example, bots often open a large number of additional connections to legitimate sites (to perform click fraud or query for the current time), and bots can deliberately produce “noise” – bogus connections that make the analysis more difficult. Thus, before one can build a model for C&C traffic or blacklist IP addresses and domains, one first has to pick the C&C connections among all the network traffic that a bot produces. In this paper, we present JACKSTRAWS, a system that accurately identifies C&C connections. To this end, we leverage host-based information that provides insights into which data is sent over each network connection as well as the ways in which a bot processes the information that it receives. More precisely, we associate with each network connection a behavior graph that captures the system calls that lead to this connection, as well as the system calls that operate on data that is returned. By using machine learning techniques and a training set of graphs that are associated with known C&C connections, we automatically extract and generalize graph templates that capture the core of different types of C&C activity. Later, we use these C&C templates to match against behavior graphs produced by other bots. Our results show that JACKSTRAWS can accurately detect C&C connections, even for novel bot families that were not used for template generation.