Branka Stojanovic

Dr. Branka Stojanovic

orcid

Research Focus & Metrics

Academic Career Length

11Years (2016-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

View All Publications
25 February 2021 in Sensors
Verified
Journal Article
Open access
PDF file
BSBranka Stojanovic
Branka Stojanovic
JBJosip Božić
Josip Božić
KHKatharina Hofer-Schmitz
Katharina Hofer-Schmitz
KNKai Nahrgang
Kai Nahrgang
AWAndreas Weber
Andreas Weber
JRJoel Runevic
Joel Runevic
Financial technology, or Fintech, represents an emerging industry on the global market. With online transactions on the rise, the use of IT for automation of financial services is of increasing importance. Fintech enables institutions to deliver services to customers worldwide on a 24/7 basis. Its services are often easy to access and enable customers to perform transactions in real-time. In fact, advantages such as these make Fintech increasingly popular among clients. However, since Fintech transactions are made up of information, ensuring security becomes a critical issue. Vulnerabilities in such systems leave them exposed to fraudulent acts, which cause severe damage to clients and providers alike. For this reason, techniques from the area of Machine Learning (ML) are applied to identify anomalies in Fintech applications. They target suspicious activity in financial datasets and generate models in order to anticipate future frauds. We contribute to this important issue and provide an evaluation on anomaly detection methods for this matter. Experiments were conducted on several fraudulent datasets from real-world and synthetic databases, respectively. The obtained results confirm that ML methods contribute to fraud detection with varying success. Therefore, we discuss the effectiveness of the individual methods with regard to the detection rate. In addition, we provide an analysis on the influence of selected features on their performance. Finally, we discuss the impact of the observed results for the security of Fintech applications in the future.

30 October 2024 in International Journal of Information Security
Verified
Journal Article
Open access
PDF file
MLMax Landauer
Max Landauer
FSFlorian Skopik
Florian Skopik
BSBranka Stojanovic
Branka Stojanovic
AFAndreas Flatscher
Andreas Flatscher
TUTorsten Ullrich
Torsten Ullrich
Understanding the current threat landscape as well as timely detection of imminent attacks are primary objectives of cyber security. Through time-series modeling of security data, such as event logs, alerts, or incidents, analysts take a step towards these goals. On the one hand, extrapolating time-series to predict future occurrences of attacks and vulnerabilities is able to support decision-making and preparation against threats. On the other hand, detection of model deviations as anomalies can point to suspicious outliers and thereby disclose cyber attacks. However, since the set of available techniques for time-series analysis is just as diverse as the research domains in the area of cyber security analytics, it can be difficult for analysts to understand which approaches fit the properties of security data at hand. This paper therefore conducts a broad literature review in research domains that leverage time-series analysis for cyber security analytics, with focus on available techniques, data sets, and challenges imposed by applications or feature properties. The results of our study indicate that relevant approaches range from detective systems ingesting short-term and low-level events to models that produce long-term forecasts of high-level attack cases.

5 July 2022 in Applied Sciences
Verified
Journal Article
Open access
PDF file
HNHelmut Neuschmied
Helmut Neuschmied
MWMartin Winter
Martin Winter
BSBranka Stojanovic
Branka Stojanovic
KHKatharina Hofer-Schmitz
Katharina Hofer-Schmitz
JBJosip Božić
Josip Božić
UKUlrike Kleb
Ulrike Kleb
In the face of emerging technological achievements, cyber security remains a significant issue. Despite the new possibilities that arise with such development, these do not come without a drawback. Attackers make use of the new possibilities to take advantage of possible security defects in new systems. Advanced-persistent-threat (APT) attacks represent sophisticated attacks that are executed in multiple steps. In particular, network systems represent a common target for APT attacks where known or yet undiscovered vulnerabilities are exploited. For this reason, intrusion detection systems (IDS) are applied to identify malicious behavioural patterns in existing network datasets. In recent times, machine-learning (ML) algorithms are used to distinguish between benign and anomalous activity in such datasets. The application of such methods, especially autoencoders, has received attention for achieving good detection results for APT attacks. This paper builds on this fact and applies several autoencoder-based methods for the detection of such attack patterns in two datasets created by combining two publicly available benchmark datasets. In addition to that, statistical analysis is used to determine features to supplement the anomaly detection process. An anomaly detector is implemented and evaluated on a combination of both datasets, including two experiment instances–APT-attack detection in an independent test dataset and in a zero-day-attack test dataset. The conducted experiments provide promising results on the plausibility of features and the performance of applied algorithms. Finally, a discussion is provided with suggestions of improvements in the anomaly detector.

3 December 2022 in Sensors
Verified
Journal Article
Open access
PDF file
BSBranka Stojanovic
Branka Stojanovic
JBJosip Božić
Josip Božić
The digitalisation of finance influenced the emergence of new technological concepts for existing user needs. Financial technology, or fintech, provides improved services for customers and new economic value for businesses. As such, fintech services require on-demand availability on a 24/7 basis. For this reason, they are often deployed in cloud environments that allow connectivity with ubiquitous devices. This allows customers to perform online transactions, which are overseen by the respective financial institutions. However, such cloud-based systems introduce new challenges for information security. On one hand, they represent attractive targets for cyberattacks. On the other, financial frauds can still go unnoticed by the financial institutions in charge. This paper contributes to both challenges by introducing the concept for a cloud-based system architecture for fraud detection and client profiling in the banking domain. Therefore, a systematic risk assessment was conducted in this context, and exploitation probabilities were inferred for multiple attack scenarios. In addition, formal verification was accomplished in order to determine the effects of successful vulnerability exploits. The consequences of such security violations are discussed, and considerations are given for improving the resilience of fintech systems.

1 June 2021 in Applied Sciences
Verified
Journal Article
Open access
PDF file
HVHeribert Vallant
Heribert Vallant
BSBranka Stojanovic
Branka Stojanovic
JBJosip Božić
Josip Božić
KHKatharina Hofer-Schmitz
Katharina Hofer-Schmitz
Smart Grids (SGs) represent electrical power systems that incorporate increased information processing and efficient technological solutions. The integration of local prosumers, demand response systems and storage allows novel possibilities with regard to energy balancing and optimization of grid operations. Unfortunately, the dependence on IT leaves the SG exposed to security violations. In this paper, we contribute to this challenge and provide a methodology for systematic risk assessment of cyber attacks in SG systems. We propose a threat model and identify possible vulnerabilities in low-voltage distribution grids. Then, we calculate exploitation probabilities from realistic attack scenarios. Lastly, we apply formal verification to check the stochastic model against attack properties. The obtained results provide insight into potential threats and the likeliness of successful attacks. We elaborate on the effects of a security violation with regard to security and privacy of energy clients. In the aftermath, we discuss future considerations for improving security in the critical energy sector.

17 March 2021 in Electronics
Verified
Journal Article
Open access
PDF file
KHKatharina Hofer-Schmitz
Katharina Hofer-Schmitz
UKUlrike Kleb
Ulrike Kleb
BSBranka Stojanovic
Branka Stojanovic
This paper investigates the influences of different statistical network traffic feature sets on detecting advanced persistent threats. The selection of suitable features for detecting targeted cyber attacks is crucial to achieving high performance and to address limited computational and storage costs. The evaluation was performed on a semi-synthetic dataset, which combined the CICIDS2017 dataset and the Contagio malware dataset. The CICIDS2017 dataset is a benchmark dataset in the intrusion detection field and the Contagio malware dataset contains real advanced persistent threat (APT) attack traces. Several different combinations of datasets were used to increase variety in background data and contribute to the quality of results. For the feature extraction, the CICflowmeter tool was used. For the selection of suitable features, a correlation analysis including an in-depth feature investigation by boxplots is provided. Based on that, several suitable features were allocated into different feature sets. The influences of these feature sets on the detection capabilities were investigated in detail with the local outlier factor method. The focus was especially on attacks detected with different feature sets and the influences of the background on the detection capabilities with respect to the local outlier factor method. Based on the results, we could determine a superior feature set, which detected most of the malicious flows.