arXiv subjects

Steffen Wendzel

Publications and source records attributed to Steffen Wendzel.

At least 19 recordsLinked to original sources

arXiv2025

Silence Speaks Volumes: A New Paradigm for Covert Communication via History Timing Patterns

A Covert Channel (CC) exploits legitimate communication mechanisms to stealthily transmit information, often bypassing traditional security controls. Among these, a novel paradigm called History Covert Channels (HCC) leverages past network events as reference points to embed covert messages. Unlike traditional timing- or storage-based CCs, which directly manipulate traffic patterns or packet contents, HCCs minimize detectability by encoding information through small pointers to historical data. This approach enables them to amplify the size of transmitted covert data by referring to more bits than are actually embedded. Recent research has explored the feasibility of such methods, demonstrating their potential to evade detection by repurposing naturally occurring network behaviors as a covert transmission medium. This paper introduces a novel method for establishing and maintaining covert communication links using relative pointers to network timing patterns, which minimizes the reliance of the HCC on centralized timekeeping and reduces the likelihood of being detected by standard network monitoring tools. We also explore the tailoring of HCCs to optimize their robustness and undetectability characteristics. Our experiments reveal a better bitrate compared to previous work.

cs.CR↗

arXiv2025

Improving the Identification of Real-world Malware's DNS Covert Channels Using Locality Sensitive Hashing

Nowadays, malware increasingly uses DNS-based covert channels in order to evade detection and maintain stealthy communication with its command-and-control servers. While prior work has focused on detecting such activity, identifying specific malware families and their behaviors from captured network traffic remains challenging due to the variability of DNS. In this paper, we present the first application of Locality Sensitive Hashing to the detection and identification of real-world malware utilizing DNS covert channels. Our approach encodes DNS subdomain sequences into statistical similarity features that effectively capture anomalies indicative of malicious activity. Combined with a Random Forest classifier, our method achieves higher accuracy and reduced false positive rates than prior approaches, while demonstrating improved robustness and generalization to previously unseen or modified malware samples. We further demonstrate that our approach enables reliable classification of malware behavior (e.g., uploading or downloading of files), based solely on DNS subdomains.

cs.CR↗

arXiv2025

Combining Different Existing Methods for Describing Steganography Hiding Methods

The proliferation of digital carriers that can be exploited to conceal arbitrary data has greatly increased the number of techniques for implementing network steganography. As a result, the literature overlaps greatly in terms of concepts and terminology. Moreover, from a cybersecurity viewpoint, the same hiding mechanism may be perceived differently, making harder the development of a unique defensive strategy or the definition of practices to mitigate risks arising from the use of steganography. To mitigate these drawbacks, several researchers introduced approaches that aid in the unified description of steganography methods and network covert channels. Understanding and combining all descriptive methods for steganography techniques is a challenging but important task. For instance, researchers might want to explain how malware applies a certain steganography technique or categorize a novel hiding approach. Consequently, this paper aims to provide an introduction to the concept of descriptive methods for steganography. The paper is organized in the form of a tutorial, with the main goal of explaining how existing descriptions and taxonomy objects can be combined to achieve a detailed categorization and description of hiding methods. To show how this can effectively help the research community, the paper also contains various real-world examples.

cs.CR↗

arXiv2025

Domainator: Detecting and Identifying DNS-Tunneling Malware Using Metadata Sequences

In recent years, malware with tunneling (or: covert channel) capabilities is on the rise. While malware research led to several methods and innovations, the detection and differentiation of malware solely based on its DNS tunneling features is still in its infancy. Moreover, no work so far has used the DNS tunneling traffic to gain knowledge over the current actions taken by the malware. In this paper, we present Domainator, an approach to detect and differentiate state-of-the-art malware and DNS tunneling tools without relying on trivial (but quickly altered) features such as "magic bytes" that are embedded into subdomains. Instead, we apply an analysis of sequential patterns to identify specific types of malware. We evaluate our approach with 7 different malware samples and tunneling tools and can identify the particular malware based on its DNS traffic. We further infer the rough behavior of the particular malware through its DNS tunneling artifacts. Finally, we compare our Domainator with related methods.

cs.CR↗

arXiv2025

A Survey of Internet Censorship and its Measurement: Methodology, Trends, and Challenges

Internet censorship limits the access of nodes residing within a specific network environment to the public Internet, and vice versa. During the last decade, techniques for conducting Internet censorship have been developed further. Consequently, methodology for measuring Internet censorship had been improved as well. In this paper, we firstly provide a survey of network-level Internet censorship techniques. Secondly, we survey censorship measurement methodology. We further cover the censorship of circumvention tools and its measurement, as well as available datasets. In cases where it is beneficial, we bridge the terminology and taxonomy of Internet censorship with related domains, namely traffic obfuscation and information hiding. We further extend the technical perspective with recent trends and challenges, including human aspects of Internet censorship.

cs.CR↗

arXiv2024

DYST (Did You See That?): An Amplified Covert Channel That Points To Previously Seen Data

Covert channels are stealthy communication channels that enable manifold adversary and legitimate scenarios, ranging from malware communications to the exchange of confidential information by journalists and censorship circumvention. We introduce a new class of covert channels that we call history covert channels. We further present a new paradigm: covert channel amplification. All covert channels described until now need to craft seemingly legitimate flows or need to modify third-party flows, mimicking unsuspicious behavior. In contrast, history covert channels can communicate by pointing to unaltered legitimate traffic created by regular network nodes. Only a negligible fraction of the covert communication process requires the transfer of covert information by the covert channel's sender. This information can be sent through different protocols/channels. Our approach allows an amplification of the covert channel's message size, i.e., minimizing the fraction of actually transferred secret data by a covert channel's sender in relation to the overall secret data being exchanged. Further, we extend the current taxonomy for covert channels to show how history channels can be categorized. We describe multiple scenarios in which history covert channels can be realized, analyze the characteristics of these channels, and show how their configuration can be optimized.

cs.CR↗

arXiv2023

Exploration of Differentiability in a Proton Computed Tomography Simulation Framework

Objective. Algorithmic differentiation (AD) can be a useful technique to numerically optimize design and algorithmic parameters by, and quantify uncertainties in, computer simulations. However, the effectiveness of AD depends on how "well-linearizable" the software is. In this study, we assess how promising derivative information of a typical proton computed tomography (pCT) scan computer simulation is for the aforementioned applications. Approach. This study is mainly based on numerical experiments, in which we repeatedly evaluate three representative computational steps with perturbed input values. We support our observations with a review of the algorithmic steps and arithmetic operations performed by the software, using debugging techniques. Main results. The model-based iterative reconstruction (MBIR) subprocedure (at the end of the software pipeline) and the Monte Carlo (MC) simulation (at the beginning) were piecewise differentiable. Jumps in the MBIR function arose from the discrete computation of the set of voxels intersected by a proton path. Jumps in the MC function likely arose from changes in the control flow that affect the amount of consumed random numbers. The tracking algorithm solves an inherently non-differentiable problem. Significance. The MC and MBIR codes are ready for the integration of AD, and further research on surrogate models for the tracking subprocedure is necessary.

physics.med-ph↗

arXiv2021

Adaptive Warden Strategy for Countering Network Covert Storage Channels

The detection and elimination of covert channels are performed by a network node, known as a warden. Especially if faced with adaptive covert communication parties, a regular warden equipped with a static set of normalization rules is ineffective compared to a dynamic warden. However, dynamic wardens rely on periodically changing rule sets and have their own limitations, since they do not consider traffic specifics. We propose a novel adaptive warden strategy, capable of selecting active normalization rules by taking into account the characteristics of the observed network traffic. Our goal is to disturb the covert channel and provoke the covert peers to expose themselves more by increasing the number of packets required to perform a successful covert data transfer. Our evaluation revealed that the adaptive warden has better efficiency and effectiveness when compared to the dynamic warden because of its adaptive selection of normalization rules.

cs.CR↗

arXiv2021

A Revised Taxonomy of Steganography Embedding Patterns

Steganography embraces several hiding techniques which spawn across multiple domains. However, the related terminology is not unified among the different domains, such as digital media steganography, text steganography, cyber-physical systems steganography, network steganography (network covert channels), local covert channels, and out-of-band covert channels. To cope with this, a prime attempt has been done in 2015, with the introduction of the so-called hiding patterns, which allow to describe hiding techniques in a more abstract manner. Despite significant enhancements, the main limitation of such a taxonomy is that it only considers the case of network steganography. Therefore, this paper reviews both the terminology and the taxonomy of hiding patterns as to make them more general. Specifically, hiding patterns are split into those that describe the embedding and the representation of hidden data within the cover object. As a first research action, we focus on embedding hiding patterns and we show how they can be applied to multiple domains of steganography instead of being limited to the network scenario. Additionally, we exemplify representation patterns using network steganography. Our pattern collection is available under https://patterns.ztt.hs-worms.de.

cs.CR↗

arXiv2021

Countering Adaptive Network Covert Communication with Dynamic Wardens

Network covert channels are hidden communication channels in computer networks. They influence several factors of the cybersecurity economy. For instance, by improving the stealthiness of botnet communications, they aid and preserve the value of darknet botnet sales. Covert channels can also be used to secretly exfiltrate confidential data out of organizations, potentially resulting in loss of market/research advantage. Considering the above, efforts are needed to develop effective countermeasures against such threats. Thus in this paper, based on the introduced novel warden taxonomy, we present and evaluate a new concept of a dynamic warden. Its main novelty lies in the modification of the warden's behavior over time, making it difficult for the adaptive covert communication parties to infer its strategy and perform a successful hidden data exchange. Obtained experimental results indicate the effectiveness of the proposed approach.

cs.CR↗

arXiv2021

Protocol-independent Detection of "Messaging Ordering" Network Covert Channels

Detection methods are available for several known covert channels. However, a type of covert channel that received little attention within the last decade is the "message ordering" channel. Such a covert channel changes the order of PDUs (protocol data units, i.e. packets) transferred over the network to encode hidden information. The advantage of these channels is that they cannot be blocked easily as they do not modify header content but instead mimic typical network behavior such as TCP segments that arrive in a different order than they were sent. Contribution: In this paper, we show a protocol-independent approach to detect message ordering channels. Our approach is based on a modified compressibility score. We analyze the detectability of message ordering channels and whether several types of message ordering channels differ in their detectability. Results: Our results show that the detection of message ordering channels depends on their number of utilized PDUs. First, we performed a rough threshold selection by hand, which we later optimized using the C4.5 decision tree classifier. We were able to detect message ordering covert channels with an accuracy and F1 score of >= 99.5% and a false-positive rate < 1% and < 0.1% if they use sequences of 3 or 4 PDUs, respectively. Simpler channels that only manipulate a sequence of two PDUs were detectable with an accuracy and F1 score of 94.5% and were linked to a false-positive rate of 5.19%. We thus consider our approach suitable for real-world detection scenarios with channels utilizing 3 or 4 PDUs while the detection of channels utilizing 2 PDUs should be improved further.

cs.CR↗

arXiv2017

Unified Description for Network Information Hiding Methods

Until now hiding methods in network steganography have been described in arbitrary ways, making them difficult to compare. For instance, some publications describe classical channel characteristics, such as robustness and bandwidth, while others describe the embedding of hidden information. We introduce the first unified description of hiding methods in network steganography. Our description method is based on a comprehensive analysis of the existing publications in the domain. When our description method is applied by the research community, future publications will be easier to categorize, compare and extend. Our method can also serve as a basis to evaluate the novelty of hiding methods proposed in the future.

cs.CR↗

arXiv2016

Why Johnny Can't Use Stego: a Human-oriented Perspective on the Application of Steganography

Steganography is the discipline that deals with concealing the existence of secret communications. Existing research already provided several fundamentals for defining steganography and presented a multitude of hiding methods and countermeasures for this research discipline. We identified that no work exists that discusses the process of applying steganography from an individual's perspective. This paper presents a phase model that explains pre-conditions of applying steganography as well as the decision-making process and the final termination of a steganographic communication. The model can be used to explain whether an individual can use steganography and to explain whether and why an individual desires to use steganography. Moreover, the model can be used in research publications to indicate the addressed model's phase of scientific contributions. Furthermore, our model can be used to teach the process of steganography-application to students.

cs.CR↗

arXiv2015

Creativity in Mind: Evaluating and Maintaining Advances in Network Steganographic Research

The research discipline of network steganography deals with the hiding of information within network transmissions, e.g. to transfer illicit information in networks with Internet censorship. The last decades of research on network steganography led to more than hundred techniques for hiding data in network transmissions. However, previous research has shown that most of these hiding techniques are either based on the same idea or introduce limited novelty, enabling the application of existing countermeasures. In this paper, we provide a link between the field of creativity and network steganographic research. We propose a framework and a metric to help evaluating the creativity bound to a given hiding technique. This way, we support two sides of the scientific peer review process as both authors and reviewers can use our framework to analyze the novelty and applicability of hiding techniques. At the same time, we contribute to a uniform terminology in network steganography.

cs.MM↗

arXiv2015

"The Good, The Bad And The Ugly": Evaluation of Wi-Fi Steganography

In this paper we propose a new method for the evaluation of network steganography algorithms based on the new concept of "the moving observer". We considered three levels of undetectability named: "good", "bad", and "ugly". To illustrate this method we chose Wi-Fi steganography as a solid family of information hiding protocols. We present the state of the art in this area covering well-known hiding techniques for 802.11 networks. "The moving observer" approach could help not only in the evaluation of steganographic algorithms, but also might be a starting point for a new detection system of network steganography. The concept of a new detection system, called MoveSteg, is explained in detail.

cs.MM↗

arXiv2015

Micro protocol engineering for unstructured carriers: On the embedding of steganographic control protocols into audio transmissions

Network steganography conceals the transfer of sensitive information within unobtrusive data in computer networks. So-called micro protocols are communication protocols placed within the payload of a network steganographic transfer. They enrich this transfer with features such as reliability, dynamic overlay routing, or performance optimization --- just to mention a few. We present different design approaches for the embedding of hidden channels with micro protocols in digitized audio signals under consideration of different requirements. On the basis of experimental results, our design approaches are compared, and introduced into a protocol engineering approach for micro protocols.

cs.MM↗

arXiv2015

A Pattern-based Survey and Categorization of Network Covert Channel Techniques

Network covert channels are used to hide communication inside network protocols. Within the last decades, various techniques for covert channels arose. We surveyed and analyzed 109 techniques developed between 1987 and 2013 and show that these techniques can be reduced to only 11 different patterns. Moreover, the majority (69.7%) of techniques can be categorized in only four different patterns, i.e. most of the techniques we surveyed are very similar. We represent the patterns in a hierarchical catalog using a pattern language. Our pattern catalog will serve as a base for future covert channel novelty evaluation. Furthermore, we apply the concept of pattern variations to network covert channels. With pattern variations, the context of a pattern can change. For example, a channel developed for IPv4 can automatically be adapted to other network protocols. We also propose the pattern-based covert channel optimizations pattern hopping and pattern combination. Finally, we lay the foundation for pattern-based countermeasures: While many current countermeasures were developed for specific channels, a pattern-oriented approach allows to apply one countermeasure to multiple channels. Hence, future countermeasure development can focus on patterns, and the development of real-world protection against covert channels is greatly simplified.

cs.CR↗

arXiv2015

Visualizing BACnet data to facilitate humans in building-security decision-making

Building automation systems (BAS) are interlinked networks of hardware and software, which monitor and control events in the buildings. One of the data communication protocols used in BAS is Building Automation and Control networking protocol (BACnet) which is an internationally adopted ISO standard for the communication between BAS devices. Although BAS focus on providing safety for inhabitants, decreasing the energy consumption of buildings and reducing their operational cost, their security suffers due to the inherent complexity of the modern day systems. The issues such as monitoring of BAS effectively present a significant challenge, i.e., BAS operators generally possess only partial situation awareness. Especially in large and inter-connected buildings, the operators face the challenge of spotting meaningful incidents within large amounts of simultaneously occurring events, causing the anomalies in the BAS network to go unobserved. In this paper, we present the techniques to analyze and visualize the data for several events from BAS devices in a way that determines the potential importance of such unusual events and helps with the building-security decision making. We implemented these techniques as a mobile (Android) based application for displaying application data and as tools to analyze the communication flows using directed graphs.

cs.CR↗