arXiv subjects

Koen T. W. Teuwen

Publications and source records attributed to Koen T. W. Teuwen.

4 recordsLinked to original sources

arXiv2026

How It's Made: Uncovering Detection Engineering Processes for Network Intrusion Detection Rules

Many Security Operations Centers rely on signature-based Network Intrusion Detection Systems like Suricata, yet detection rule engineering remains understudied. We investigate this process by introducing SuriCap, a platform for rule engineering exercises, and hosting CTF-style workshops where 60 participants, trained MSc students, and experienced SOC professionals, created rules for four scenarios. Participants produced 3146 valid rules, enabling analysis of their methods, performance, and iteration patterns. Surprisingly, prior experience had limited impact on rule quality, suggesting that less experienced engineers can produce rules comparable to experts. We also observed challenges in generalizing rules beyond available tests, underscoring the need for sufficient labeled data. From our study, we identify three phases and a common pattern in rule engineering, offering SOC managers insights to improve their processes and expectations of engineer expertise.

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arXiv2025

On the Effect of Ruleset Tuning and Data Imbalance on Explainable Network Security Alert Classifications: a Case-Study on DeepCASE

Automation in Security Operations Centers (SOCs) plays a prominent role in alert classification and incident escalation. However, automated methods must be robust in the presence of imbalanced input data, which can negatively affect performance. Additionally, automated methods should make explainable decisions. In this work, we evaluate the effect of label imbalance on the classification of network intrusion alerts. As our use-case we employ DeepCASE, the state-of-the-art method for automated alert classification. We show that label imbalance impacts both classification performance and correctness of the classification explanations offered by DeepCASE. We conclude tuning the detection rules used in SOCs can significantly reduce imbalance and may benefit the performance and explainability offered by alert post-processing methods such as DeepCASE. Therefore, our findings suggest that traditional methods to improve the quality of input data can benefit automation.

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arXiv2025

Ruling the Unruly: Designing Effective, Low-Noise Network Intrusion Detection Rules for Security Operations Centers

Many Security Operations Centers (SOCs) today still heavily rely on signature-based Network Intrusion Detection Systems (NIDS) such as Suricata. The specificity of intrusion detection rules and the coverage provided by rulesets are common concerns within the professional community surrounding SOCs, which impact the effectiveness of automated alert post-processing approaches. We postulate a better understanding of factors influencing the quality of rules can help address current SOC issues. In this paper, we characterize the rules in use at a collaborating commercial (managed) SOC serving customers in sectors including education and IT management. During this process, we discover six relevant design principles, which we consolidate through interviews with experienced rule designers at the SOC.We then validate our design principles by quantitatively assessing their effect on rule specificity. We find that several of these design considerations significantly impact unnecessary workload caused by rules. For instance, rules that leverage proxies for detection, and rules that do not employ alert throttling or do not distinguish (un)successful malicious actions, cause significantly more workload for SOC analysts. Moreover, rules that match a generalized characteristic to detect malicious behavior, which is believed to increase coverage, also significantly increase workload, suggesting a tradeoff must be struck between rule specificity and coverage. We show that these design principles can be applied successfully at a SOC to reduce workload whilst maintaining coverage despite the prevalence of violations of the principles.

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arXiv2024

A Modular Approach to Automatic Cyber Threat Attribution using Opinion Pools

Cyber threat attribution can play an important role in increasing resilience against digital threats. Recent research focuses on automating the threat attribution process and on integrating it with other efforts, such as threat hunting. To support increasing automation of the cyber threat attribution process, this paper proposes a modular architecture as an alternative to current monolithic automated approaches. The modular architecture can utilize opinion pools to combine the output of concrete attributors. The proposed solution increases the tractability of the threat attribution problem and offers increased usability and interpretability, as opposed to monolithic alternatives. In addition, a Pairing Aggregator is proposed as an aggregation method that forms pairs of attributors based on distinct features to produce intermediary results before finally producing a single Probability Mass Function (PMF) as output. The Pairing Aggregator sequentially applies both the logarithmic opinion pool and the linear opinion pool. An experimental validation suggests that the modular approach does not result in decreased performance and can even enhance precision and recall compared to monolithic alternatives. The results also suggest that the Pairing Aggregator can improve precision over the linear and logarithmic opinion pools. Furthermore, the improved k-accuracy in the experiment suggests that forensic experts can leverage the resulting PMF during their manual attribution processes to enhance their efficiency.

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