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An Algorithm for Anomaly-based Botnet Detection

We present an anomaly-based algorithm for detecting IRC-based botnet meshes. The algorithm combines an IRC mesh detection component with a TCP scan detection heuristic called the TCP work weight. The IRC component produces two tuples, one for determining the IRC mesh based on IP channel names, and a sub-tuple which collects statistics (including the TCP work weight) on individual IRC hosts in channels. We sort the channels by the number of scanners producing a sorted list of potential botnets. This algorithm has been deployed in PSU's DMZ for over a year and has proven effective in reducing the number of botnet clients.