Tracking and Mitigation of Malicious Remote Control Networks

Attacks against end-users are one of the negative side effects of today’s networks. The goal of the attacker is to compromise the victim’s machine and obtain control over it. This machine is then used to carry out denial-of-service attacks, to send out spam mails, or for other nefarious purposes. From an attacker’s point of view, this kind of attack is even more efficient if she manages to compromise a large number of machines in parallel. In order to control all these machines, she establishes a "malicious remote control network", i.e., a mechanism that enables an attacker the control over a large number of compromised machines for illicit activities. The most common type of these networks observed so far are so called "botnets". Since these networks are one of the main factors behind current abuses on the Internet, we need to find novel approaches to stop them in an automated and efficient way. In this thesis we focus on this open problem and propose a general root cause methodology to stop malicious remote control networks. The basic idea of our method consists of three steps. In the first step, we use "honeypots" to collect information. A honeypot is an information system resource whose value lies in unauthorized or illicit use of that resource. This technique enables us to study current attacks on the Internet and we can for example capture samples of autonomous spreading malware ("malicious software") in an automated way. We analyze the collected data to extract information about the remote control mechanism in an automated fashion. For example, we utilize an automated binary analysis tool to find the Command & Control (C&C) server that is used to send commands to the infected machines. In the second step, we use the extracted information to infiltrate the malicious remote control networks. This can for example be implemented by impersonating as a bot and infiltrating the remote control channel. Finally, in the third step we use the information collected during the infiltration phase to mitigate the network, e.g., by shutting down the remote control channel such that the attacker cannot send commands to the compromised machines. In this thesis we show the practical feasibility of this method. We examine different kinds of malicious remote control networks and discuss how we can track all of them in an automated way. As a first example, we study botnets that use a central C&C server: We illustrate how the three steps can be implemented in practice and present empirical measurement results obtained on the Internet. Second, we investigate botnets that use a peer-to-peer based communication channel. Mitigating these botnets is harder since no central C&C server exists which could be taken offline. Nevertheless, our methodology can also be applied to this kind of networks and we present empirical measurement results substantiating our method. Third, we study fast-flux service networks. The idea behind these networks is that the attacker does not directly abuse the compromised machines, but uses them to establish a proxy network on top of these machines to enable a robust hosting infrastructure. Our method can be applied to this novel kind of malicious remote control networks and we present empirical results supporting this claim. We anticipate that the methodology proposed in this thesis can also be used to track and mitigate other kinds of malicious remote control networks

On Detection of Current and Next-Generation Botnets.

Botnets are one of the most serious security threats to the Internet and its end users. A botnet consists of compromised computers that are remotely coordinated by a botmaster under a Command and Control (C&C) infrastructure. Driven by financial incentives, botmasters leverage botnets to conduct various cybercrimes such as spamming, phishing, identity theft and Distributed-Denial-of-Service (DDoS) attacks. There are three main challenges facing botnet detection. First, code obfuscation is widely employed by current botnets, so signature-based detection is insufficient. Second, the C&C infrastructure of botnets has evolved rapidly. Any detection solution targeting one botnet instance can hardly keep up with this change. Third, the proliferation of powerful smartphones presents a new platform for future botnets. Defense techniques designed for existing botnets may be outsmarted when botnets invade smartphones. Recognizing these challenges, this dissertation proposes behavior-based botnet detection solutions at three different levels---the end host, the edge network and the Internet infrastructure---from a small scale to a large scale, and investigates the next-generation botnet targeting smartphones. It (1) addresses the problem of botnet seeding by devising a per-process containment scheme for end-host systems; (2) proposes a hybrid botnet detection framework for edge networks utilizing combined host- and network-level information; (3) explores the structural properties of botnet topologies and measures network components' capabilities of large-scale botnet detection at the Internet infrastructure level; and (4) presents a proof-of-concept mobile botnet employing SMS messages as the C&C and P2P as the topology to facilitate future research on countermeasures against next-generation botnets. The dissertation makes three primary contributions. First, the detection solutions proposed utilize intrinsic and fundamental behavior of botnets and are immune to malware obfuscation and traffic encryption. Second, the solutions are general enough to identify different types of botnets, not a specific botnet instance. They can also be extended to counter next-generation botnet threats. Third, the detection solutions function at multiple levels to meet various detection needs. They each take a different perspective but are highly complementary to each other, forming an integrated botnet detection framework.Ph.D.Computer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91382/1/gracez_1.pd

Categorizing Blog Spam

The internet has matured into the focal point of our era. Its ecosystem is vast, complex, and in many regards unaccounted for. One of the most prevalent aspects of the internet is spam. Similar to the rest of the internet, spam has evolved from simply meaning ‘unwanted emails’ to a blanket term that encompasses any unsolicited or illegitimate content that appears in the wide range of media that exists on the internet. Many forms of spam permeate the internet, and spam architects continue to develop tools and methods to avoid detection. On the other side, cyber security engineers continue to develop more sophisticated detection tools to curb the harmful effects that come with spam. This virtual arms race has no end in sight. Most efforts thus far have been toward accurately detecting spam from ham, and rightfully so since initial detection is essential. However, research is lacking in understanding the current ecosystem of spam, spam campaigns, and the behavior of the botnets that drive the majority of spam traffic. This thesis focuses on characterizing spam, particularly the spam that appears in forums, where the spam is delivered by bots posing as legitimate users. Forum spam is used primarily to push advertisements or to boost other websites’ perceived popularity by including HTTP links in the content of the post. We conduct an experiment to collect a sample of the blog posts and network activity of the spambots that exist in the internet. We then present a corpora available to conduct analysis on and proceed with our own analysis. We cluster associated groups of users and IP addresses into entities, which we accept as a model of the underlying botnets that interact with our honeypots. We use Natural Language Processing (NLP) and Machine Learning (ML) to determine that creating semantic-based models of botnets are sufficient for distinguishing them from one another. We also find that the syntactic structure of posts has little variation from botnet to botnet. Finally we confirm that to a large degree botnet behavior and content hold across different domains

On the security of machine learning in malware C & C detection:a survey

One of the main challenges in security today is defending against malware attacks. As trends and anecdotal evidence show, preventing these attacks, regardless of their indiscriminate or targeted nature, has proven difficult: intrusions happen and devices get compromised, even at security-conscious organizations. As a consequence, an alternative line of work has focused on detecting and disrupting the individual steps that follow an initial compromise and are essential for the successful progression of the attack. In particular, several approaches and techniques have been proposed to identify the command and control (C&C) channel that a compromised system establishes to communicate with its controller. A major oversight of many of these detection techniques is the design's resilience to evasion attempts by the well-motivated attacker. C&C detection techniques make widespread use of a machine learning (ML) component. Therefore, to analyze the evasion resilience of these detection techniques, we first systematize works in the field of C&C detection and then, using existing models from the literature, go on to systematize attacks against the ML components used in these approaches

Cyber warfare and autonomous self-defence

The last two decades have witnessed increased activity by states within the ‘fifth dimension’ (cyberspace) to conduct both civilian and military operations. It is now over two decades since Arquilla and Ronfeldt warned about the advent of cyber warfare in the foreseeable future, and cyberspace has now become a primary battlefield. Prevailing at the forefront of academic scrutiny within the jus ad bellum context is the extent to which cyber operations fall within the paradigm of Article 2(4) of the United Nations Charter. A traditional and restrictive interpretation of the cornerstone prohibition contained in Article 2(4) would conclude that the type of force (either threatened or actual) would need to be military / kinetic, thus potentially excluding the possibility of cyber activities. Naturally, some states would contest that it is the consequence suffered rather than the modality of attack. In turn, this raises issues as to whether or not the injury suffered by a state subjected to a cyber attack would be sufficient to invoke its inherent right of self-defence. The scope of this article is to consider the natural technological trajectory of self-defence in cyber operations by examining the very real possibility that computer networks may be enabled to eventually seek to automatically defend themselves against more aggressive cyber intrusions—‘automated cyber self-defence’. This would therefore necessitate an examination of the way and extent to which such actions would fall within the existing framework regulating a defensive response. More controversially, the article will also assert that the temporal parameters of self-defence in response to a cyber attack may need re-calibration—issues of detection (particularly against dormant malware etc.) and attribution would prevent a state from responding in a more conventional timeframe. Would self-defence therefore be permissible or indeed desirable several months after an attack has occurred if it is only then attribution becomes clear

BotChase: Graph-Based Bot Detection Using Machine Learning

Bot detection using machine learning (ML), with network flow-level features, has been extensively studied in the literature. However, existing flow-based approaches typically incur a high computational overhead and do not completely capture the network communication patterns, which can expose additional aspects of malicious hosts. Recently, bot detection systems which leverage communication graph analysis using ML have gained traction to overcome these limitations. A graph-based approach is rather intuitive, as graphs are true representations of network communications. In this thesis, we propose BotChase, a two-phased graph-based bot detection system that leverages both unsupervised and supervised ML. The first phase prunes presumable benign hosts, while the second phase achieves bot detection with high precision. Our prototype implementation of BotChase detects multiple types of bots and exhibits robustness to zero-day attacks. It also accommodates different network topologies and is suitable for large-scale data. Compared to the state-of-the-art, BotChase outperforms an end-to-end system that employs flow-based features and performs particularly well in an online setting

Large-Scale Emulation of Anonymous Communication Networks

Tor is the most popular low-latency anonymous communication system for the Internet, helping people to protect their privacy online and circumvent Internet censorship. Its low- latency anonymity and distributed design present a variety of open research questions related to — but not limited to — anonymity, performance, and scalability, that have generated considerable interest in the research community. Testing changes to the design of the protocol or studying attacks against it in the live network is undesirable as doing so can invade the privacy of users and even put them in harm’s way. Traditional Tor research has been limited to emulating a few hundred nodes with the ModelNet network emulator, or, simulating thousands of nodes with the Shadow discrete-event simulator, both of which may not accurately represent the real-world Tor network. We present SNEAC (Scalable Network Emulator for Anonymous Communication; pronounced "sneak"), a large-scale network emulator that allows us to emulate a network with thousands of nodes. Our hope is that with such large-scale experimentation, we can more closely emulate the live Tor network with half a million users