C3PO: Large-Scale Study of Covert Monitoring of C&C Servers via Over-Permissioned Protocol Infiltration

Abstract

Current techniques to monitor botnets towards disruption or takedown are likely to result in inaccurate data gathered about the botnet or be detected by C& C orchestrators. Seeking a covert and scalable solution, we look to an evolving pattern in modern malware that integrates standardized over-permissioned protocols, exposing privileged access to C&C servers. We implement techniques to detect and exploit these protocols from over-permissioned bots toward covert C&C server monitoring. Our empirical study of 200k malware captured since 2006 revealed 62,202 over-permissioned bots (nearly 1 in 3) and 443,905 C&C monitoring capabilities, with a steady increase of over-permissioned protocol use over the last 15 years. Due to their ubiquity, we conclude that even though over-permissioned protocols allow for C&C server infiltration, the efficiency and ease of use they provide continue to make them prevalent in the malware operational landscape. This paper presents C3PO, a pipeline that enables our study and empowers incident responders to automatically identify over-permissioned protocols, infiltration vectors to spoof bot-to-C&C communication, and C&C monitoring capabilities that guide covert monitoring post infiltration. Our findings suggest the over-permissioned protocol weakness provides a scalable approach to covertly monitor C&C servers, which is a fundamental enabler of botnet disruptions and takedowns.