Command & Control: Understanding, Denying and Detecting - A review of malware C2 techniques, detection and defences

In this survey, we first briefly review the current state of cyber attacks, highlighting significant recent changes in how and why such attacks are performed. We then investigate the mechanics of malware command and control (C2) establishment: we provide a comprehensive review of the techniques used by attackers to set up such a channel and to hide its presence from the attacked parties and the security tools they use. We then switch to the defensive side of the problem, and review approaches that have been proposed for the detection and disruption of C2 channels. We also map such techniques to widely-adopted security controls, emphasizing gaps or limitations (and success stories) in current best practices.Comment: Work commissioned by CPNI, available at c2report.org. 38 pages. Listing abstract compressed from version appearing in repor

Unsupervised host behavior classification from connection patterns

International audienceA novel host behavior classification approach is proposed as a preliminary step toward traffic classification and anomaly detection in network communication. Though many attempts described in the literature were devoted to flow or application classifications, these approaches are not always adaptable to operational constraints of traffic monitoring (expected to work even without packet payload, without bidirectionality, on highspeed networks or from flow reports only...). Instead, the classification proposed here relies on the leading idea that traffic is relevantly analyzed in terms of host typical behaviors: typical connection patterns of both legitimate applications (data sharing, downloading,...) and anomalous (eventually aggressive) behaviors are obtained by profiling traffic at the host level using unsupervised statistical classification. Classification at the host level is not reducible to flow or application classification, and neither is the contrary: they are different operations which might have complementary roles in network management. The proposed host classification is based on a nine-dimensional feature space evaluating host Internet connectivity, dispersion and exchanged traffic content. A Minimum Spanning Tree (MST) clustering technique is developed that does not require any supervised learning step to produce a set of statistically established typical host behaviors. Not relying on a priori defined classes of known behaviors enables the procedure to discover new host behaviors, that potentially were never observed before. This procedure is applied to traffic collected over the entire year 2008 on a transpacific (Japan/USA) link. A cross-validation of this unsupervised classification against a classical port-based inspection and a state-of-the-art method provides assessment of the meaningfulness and the relevance of the obtained classes for host behaviors

MAGMA network behavior classifier for malware traffic

Malware is a major threat to security and privacy of network users. A large variety of malware is typically spread over the Internet, hiding in benign traffic. New types of malware appear every day, challenging both the research community and security companies to improve malware identification techniques. In this paper we present MAGMA, MultilAyer Graphs for MAlware detection, a novel malware behavioral classifier. Our system is based on a Big Data methodology, driven by real-world data obtained from traffic traces collected in an operational network. The methodology we propose automatically extracts patterns related to a specific input event, i.e., a seed, from the enormous amount of events the network carries. By correlating such activities over (i) time, (ii) space, and (iii) network protocols, we build a Network Connectivity Graph that captures the overall “network behavior” of the seed. We next extract features from the Connectivity Graph and design a supervised classifier. We run MAGMA on a large dataset collected from a commercial Internet Provider where 20,000 Internet users generated more than 330 million events. Only 42,000 are flagged as malicious by a commercial IDS, which we consider as an oracle. Using this dataset, we experimentally evaluate MAGMA accuracy and robustness to parameter settings. Results indicate that MAGMA reaches 95% accuracy, with limited false positives. Furthermore, MAGMA proves able to identify suspicious network events that the IDS ignored

Scalable Techniques for Anomaly Detection

Computer networks are constantly being attacked by malicious entities for various reasons. Network based attacks include but are not limited to, Distributed Denial of Service (DDoS), DNS based attacks, Cross-site Scripting (XSS) etc. Such attacks have exploited either the network protocol or the end-host software vulnerabilities for perpetration. Current network traffic analysis techniques employed for detection and/or prevention of these anomalies suffer from significant delay or have only limited scalability because of their huge resource requirements. This dissertation proposes more scalable techniques for network anomaly detection. We propose using DNS analysis for detecting a wide variety of network anomalies. The use of DNS is motivated by the fact that DNS traffic comprises only 2-3% of total network traffic reducing the burden on anomaly detection resources. Our motivation additionally follows from the observation that almost any Internet activity (legitimate or otherwise) is marked by the use of DNS. We propose several techniques for DNS traffic analysis to distinguish anomalous DNS traffic patterns which in turn identify different categories of network attacks. First, we present MiND, a system to detect misdirected DNS packets arising due to poisoned name server records or due to local infections such as caused by worms like DNSChanger. MiND validates misdirected DNS packets using an externally collected database of authoritative name servers for second or third-level domains. We deploy this tool at the edge of a university campus network for evaluation. Secondly, we focus on domain-fluxing botnet detection by exploiting the high entropy inherent in the set of domains used for locating the Command and Control (C&C) server. We apply three metrics namely the Kullback-Leibler divergence, the Jaccard Index, and the Edit distance, to different groups of domain names present in Tier-1 ISP DNS traces obtained from South Asia and South America. Our evaluation successfully detects existing domain-fluxing botnets such as Conficker and also recognizes new botnets. We extend this approach by utilizing DNS failures to improve the latency of detection. Alternatively, we propose a system which uses temporal and entropy-based correlation between successful and failed DNS queries, for fluxing botnet detection. We also present an approach which computes the reputation of domains in a bipartite graph of hosts within a network, and the domains accessed by them. The inference technique utilizes belief propagation, an approximation algorithm for marginal probability estimation. The computation of reputation scores is seeded through a small fraction of domains found in black and white lists. An application of this technique, on an HTTP-proxy dataset from a large enterprise, shows a high detection rate with low false positive rates