Firewall resistance to metaferography in network communications

In recent years corporations and other enterprises have seen a consolidation of security services on the network perimeter. Services that have traditionally been stand-alone, such as content filtering and antivirus scanning, are pushing their way to the edge and running on security gateways such as firewalls. As a result, firewalls have transitioned from devices that protect availability by preventing denial-of-service to devices that are also responsible for protecting the confidentiality and integrity of data. However, little, if any, practical research has been done on the ability of existing technical controls such as firewalls to detect and prevent covert channels. The experiment in this thesis has been designed to evaluate the effectiveness of firewalls—specifically application-layer firewalls—in detecting, correcting, and preventing covert channels. Several application-layer HTTP covert channel tools, including Wsh and CCTT (both storage channels), as well as Leaker/Recover (a timing channel), are tested using the 7-layer OSI Network Model as a framework for analysis. This thesis concludes that with a priori knowledge of the covert channel and proper signatures, application-layer firewalls can detect both storage and timing channels. Without a priori knowledge of the covert channel, either a heuristic-based or a behavioral-based detection technique would be required. In addition, this thesis demonstrates that application-layer firewalls inherently resist covert channels by adhering to strict type enforcement of RFC standards. This thesis also asserts that metaferography is a more appropriate term than covert channels to describe the study of “carried writing” since metaferography is consistent with the etymology and naming convention of the other main branches of information hiding—namely cryptography and steganography

Machine Learning based Anomaly Detection for Cybersecurity Monitoring of Critical Infrastructures

openManaging critical infrastructures requires to increasingly rely on Information and Communi- cation Technologies. The last past years showed an incredible increase in the sophistication of attacks. For this reason, it is necessary to develop new algorithms for monitoring these infrastructures. In this scenario, Machine Learning can represent a very useful ally. After a brief introduction on the issue of cybersecurity in Industrial Control Systems and an overview of the state of the art regarding Machine Learning based cybersecurity monitoring, the present work proposes three approaches that target different layers of the control network architecture. The first one focuses on covert channels based on the DNS protocol, which can be used to establish a command and control channel, allowing attackers to send malicious commands. The second one focuses on the field layer of electrical power systems, proposing a physics-based anomaly detection algorithm for Distributed Energy Resources. The third one proposed a first attempt to integrate physical and cyber security systems, in order to face complex threats. All these three approaches are supported by promising results, which gives hope to practical applications in the next future.openXXXIV CICLO - SCIENZE E TECNOLOGIE PER L'INGEGNERIA ELETTRONICA E DELLE TELECOMUNICAZIONI - Elettromagnetismo, elettronica, telecomunicazioniGaggero, GIOVANNI BATTIST

Non-Trivial Off-Path Network Measurements without Shared Side-Channel Resource Exhaustion

Most traditional network measurement scans and attacks are carried out through the use of direct, on-path network packet transmission. This requires that a machine be on-path (i.e, involved in the packet transmission process) and as a result have direct access to the data packets being transmitted. This limits network scans and attacks to situations where access can be gained to an on-path machine. If, for example, a researcher wanted to measure the round trip time between two machines they did not have access to, traditional scans would be of little help as they require access to an on-path machine to function. Instead the researcher would need to use an off-path measurement scan. Prior work using network side-channels to perform off-path measurements or attacks relied on techniques that either exhausted the shared, finite resource being used as a side-channel or only measured basic features such as connectivity. The work presented in this dissertation takes a different approach to using network side-channels. I describe research that carries out network side-channel measurements that are more complex than connectivity, such as packet round-trip-time or detecting active TCP connections, and do not require a shared, finite resource be fully exhausted to cause information to leak via a side-channel. My work is able to accomplish this by understanding the ways in which internal network stack state changes cause observable behavior changes from the machine. The goal of this dissertation is to show that: Information side-channels can be modulated to take advantage of dependent, network state behavior to enable non-trivial, off-path measurements without fully exhausting the shared, finite resources they use

Secure covert communications over streaming media using dynamic steganography

Streaming technologies such as VoIP are widely embedded into commercial and industrial applications, so it is imperative to address data security issues before the problems get really serious. This thesis describes a theoretical and experimental investigation of secure covert communications over streaming media using dynamic steganography. A covert VoIP communications system was developed in C++ to enable the implementation of the work being carried out. A new information theoretical model of secure covert communications over streaming media was constructed to depict the security scenarios in streaming media-based steganographic systems with passive attacks. The model involves a stochastic process that models an information source for covert VoIP communications and the theory of hypothesis testing that analyses the adversary‘s detection performance. The potential of hardware-based true random key generation and chaotic interval selection for innovative applications in covert VoIP communications was explored. Using the read time stamp counter of CPU as an entropy source was designed to generate true random numbers as secret keys for streaming media steganography. A novel interval selection algorithm was devised to choose randomly data embedding locations in VoIP streams using random sequences generated from achaotic process. A dynamic key updating and transmission based steganographic algorithm that includes a one-way cryptographical accumulator integrated into dynamic key exchange for covert VoIP communications, was devised to provide secure key exchange for covert communications over streaming media. The discrete logarithm problem in mathematics and steganalysis using t-test revealed the algorithm has the advantage of being the most solid method of key distribution over a public channel. The effectiveness of the new steganographic algorithm for covert communications over streaming media was examined by means of security analysis, steganalysis using non parameter Mann-Whitney-Wilcoxon statistical testing, and performance and robustness measurements. The algorithm achieved the average data embedding rate of 800 bps, comparable to other related algorithms. The results indicated that the algorithm has no or little impact on real-time VoIP communications in terms of speech quality (< 5% change in PESQ with hidden data), signal distortion (6% change in SNR after steganography) and imperceptibility, and it is more secure and effective in addressing the security problems than other related algorithms

Traffic Analysis Resistant Infrastructure

Network traffic analysis is using metadata to infer information from traffic flows. Network traffic flows are the tuple of source IP, source port, destination IP, and destination port. Additional information is derived from packet length, flow size, interpacket delay, Ja3 signature, and IP header options. Even connections using TLS leak site name and cipher suite to observers. This metadata can profile groups of users or individual behaviors. Statistical properties yield even more information. The hidden Markov model can track the state of protocols where each state transition results in an observation. Format Transforming Encryption (FTE) encodes data as the payload of another protocol. The emulated protocol is called the host protocol. Observation-based FTE is a particular case of FTE that uses real observations from the host protocol for the transformation. By communicating using a shared dictionary according to the predefined protocol, it can difficult to detect anomalous traffic. Combining observation-based FTEs with hidden Markov models (HMMs) emulates every aspect of a host protocol. Ideal host protocols would cause significant collateral damage if blocked (protected) and do not contain dynamic handshakes or states (static). We use protected static protocols with the Protocol Proxy--a proxy that defines the syntax of a protocol using an observation-based FTE and transforms data to payloads with actual field values. The Protocol Proxy massages the outgoing packet\u27s interpacket delay to match the host protocol using an HMM. The HMM ensure the outgoing traffic is statistically equivalent to the host protocol. The Protocol Proxy is a covert channel, a method of communication with a low probability of detection (LPD). These covert channels trade-off throughput for LPD. The multipath TCP (mpTCP) Linux kernel module splits a TCP streams across multiple interfaces. Two potential architectures involve splitting a covert channel across several interfaces (multipath) or splitting a single TCP stream across multiple covert channels (multisession). Splitting a covert channel across multiple interfaces leads to higher throughput but is classified as mpTCP traffic. Splitting a TCP flow across multiple covert channels is not as performant as the previous case, but it provides added obfuscation and resiliency. Each covert channel is independent of the others, and a channel failure is recoverable. The multipath and multisession frameworks provide independently address the issues associated with covert channels. Each tool addresses a challenge. The Protocol Proxy provides anonymity in a setting were detection could have critical consequences. The mpTCP kernel module offers an architecture that increases throughput despite the channel\u27s low-bandwidth restrictions. Fusing these architectures improves the goodput of the Protocol Proxy without sacrificing the low probability of detection