arXiv subjects

Harel Berger

Publications and source records attributed to Harel Berger.

12 recordsLinked to original sources

arXiv2026

Survival of~the~Stealthiest: Evolving Low-Entropy Ransomware via~Genetic Algorithms

Traditional ransomware deployment often relies on massive encryption procedure, triggering immediate detection by modern defense systems. This work introduces a paradigm shift in cryptographic attacks by framing ransomware execution as a Search-Based Software Engineering (SBSE) optimization problem. This approach addresses the persistence gap observed in modern threats, where attacks aim to remain undercover for hours rather than minutes. Using a Genetic Algorithm (GA), we optimize data encryption under a hard constraint on the statistical deviation from baseline system activity. We demonstrate that our evolved attack patterns can evade behavioral monitors under fingerprinting techniques. Our results suggest that search-based methods provide a powerful framework for generating evasive malware, highlighting an emerging challenge for automated software defense.

cs.CR↗

arXiv2026

Mobile Apps vs. Web Browsers: A User Perception Study with Android Apps and Google Chrome

This study examines user perceptions of mobile applications (apps) versus web browsers for accessing online services, with an emphasis on security, privacy, and usability aspects. Through a combination of an experiment and a survey with Android smartphone users, the research seeks to identify the key concerns and preferences that influence their choice between mobile apps and web browsers. The findings will offer valuable insights for developers to improve the security, privacy, and usability of both platforms by addressing user concerns and misconceptions.

cs.CR↗

arXiv2026

Toward Continuous Assurance for the Democratization of AI Agent Creation in Industry

AI agents are increasingly created inside organizations by non-engineering users through low-code, no-code, and conversational development environments. This democratization enables rapid local innovation, but it also creates a reliability gap: agents that appear to users as simple productivity artifacts may depend on changing models, tools, retrieval sources, permissions, prompts, schedules, and external services. These dependencies can cause silent degradation long after deployment, even when no user directly modifies the agent. This paper identifies the reliability challenge created by democratized AI agent creation and proposes a lightweight continuous-assurance framework for citizen-created organizational agents. The framework combines dependency mapping, readiness contracts, scheduled checks, diagnostics, and lifecycle governance to assess whether an agent remains operationally ready under expected conditions. We also present an initial prototype auditor and scenario-based assessment showing how the proposed taxonomy can be translated into practical checks and actionable remediation guidance.

cs.AI↗

arXiv2026

Measuring and Evaluating the Performance of Generative AI Models for Scam Detection

Online scams continue to cause substantial financial and personal harm. As a result, detection systems based on Large Language Models (LLMs) have been integrated into security products ranging from email gateways and browser extensions to fraud-monitoring dashboards. As this adoption accelerates, a common belief has taken hold: that these models are broadly suitable for scam detection. In this work, we investigate whether LLMs, with their strong capabilities in understanding intent, context, and reasoning, can effectively detect scams across diverse scenarios without task-specific fine-tuning. We curate and release a unique benchmark dataset of real-world scams spanning multiple formats and topics. We evaluate nine LLMs of varying sizes and architectures, examining their performance under different prompting strategies and comparing them to a fine-tuned BERT-based classifier. Our results show that while larger LLMs generally outperform smaller ones, effective prompting substantially boosts the performance of smaller models. Moreover, LLMs are better at generalizing to unseen scams compared to fine-tuned models, suggesting that pre-trained knowledge contributes meaningfully to scam detection. We release our dataset and evaluation framework to facilitate future research in robust scam detection using language models.

cs.CR↗

arXiv2025

POPS: From History to Mitigation of DNS Cache Poisoning Attacks

We present a novel yet simple and comprehensive DNS cache POisoning Prevention System (POPS), designed to integrate as a module in Intrusion Prevention Systems (IPS). POPS addresses statistical DNS poisoning attacks, including those documented from 2002 to the present, and offers robust protection against similar future threats. It consists of two main components: a detection module that employs three simple rules, and a mitigation module that leverages the TC flag in the DNS header to enhance security. Once activated, the mitigation module has zero false positives or negatives, correcting any such errors on the side of the detection module. We first analyze POPS against historical DNS services and attacks, showing that it would have mitigated all network-based statistical poisoning attacks, yielding a success rate of only 0.0076% for the adversary. We then simulate POPS on traffic benchmarks (PCAPs) incorporating current potential network-based statistical poisoning attacks, and benign PCAPs; the simulated attacks still succeed with a probability of 0.0076%. This occurs because five malicious packets go through before POPS detects the attack and activates the mitigation module. In addition, POPS completes its task using only 20%-50% of the time required by other tools (e.g., Suricata or Snort), and after examining just 5%-10% as many packets. Furthermore, it successfully identifies DNS cache poisoning attacks-such as fragmentation attacks-that both Suricata and Snort fail to detect, underscoring its superiority in providing comprehensive DNS protection.

cs.CR↗

arXiv2024

Measuring DNS Censorship of Generative AI Platforms

Generative AI is an invaluable tool, however, in some parts of the world, this technology is censored due to political or societal issues. In this work, we monitor Generative AI censorship through the DNS protocol. We find China to be a leading country of Generative AI censorship. Interestingly, China does not censor all AI domain names. We also report censorship in Russia and find inconsistencies in their process. We compare our results to other measurement platforms (OONI, Censored Planet, GFWatch), and present their lack of data on Generative AI domains.

cs.CY↗

arXiv2023

Can you See me? On the Visibility of NOPs against Android Malware Detectors

Android malware still represents the most significant threat to mobile systems. While Machine Learning systems are increasingly used to identify these threats, past studies have revealed that attackers can bypass these detection mechanisms by making subtle changes to Android applications, such as adding specific API calls. These modifications are often referred to as No OPerations (NOP), which ideally should not alter the semantics of the program. However, many NOPs can be spotted and eliminated by refining the app analysis process. This paper proposes a visibility metric that assesses the difficulty in spotting NOPs and similar non-operational codes. We tested our metric on a state-of-the-art, opcode-based deep learning system for Android malware detection. We implemented attacks on the feature and problem spaces and calculated their visibility according to our metric. The attained results show an intriguing trade-off between evasion efficacy and detectability: our metric can be valuable to ensure the real effectiveness of an adversarial attack, also serving as a useful aid to develop better defenses.

cs.CR↗

arXiv2022

Problem-Space Evasion Attacks in the Android OS: a Survey

Android is the most popular OS worldwide. Therefore, it is a target for various kinds of malware. As a countermeasure, the security community works day and night to develop appropriate Android malware detection systems, with ML-based or DL-based systems considered as some of the most common types. Against these detection systems, intelligent adversaries develop a wide set of evasion attacks, in which an attacker slightly modifies a malware sample to evade its target detection system. In this survey, we address problem-space evasion attacks in the Android OS, where attackers manipulate actual APKs, rather than their extracted feature vector. We aim to explore this kind of attacks, frequently overlooked by the research community due to a lack of knowledge of the Android domain, or due to focusing on general mathematical evasion attacks - i.e., feature-space evasion attacks. We discuss the different aspects of problem-space evasion attacks, using a new taxonomy, which focuses on key ingredients of each problem-space attack, such as the attacker model, the attacker's mode of operation, and the functional assessment of post-attack applications.

cs.CR↗

arXiv2022

Do You Think You Can Hold Me? The Real Challenge of Problem-Space Evasion Attacks

Android malware is a spreading disease in the virtual world. Anti-virus and detection systems continuously undergo patches and updates to defend against these threats. Most of the latest approaches in malware detection use Machine Learning (ML). Against the robustifying effort of detection systems, raise the \emph{evasion attacks}, where an adversary changes its targeted samples so that they are misclassified as benign. This paper considers two kinds of evasion attacks: feature-space and problem-space. \emph{Feature-space} attacks consider an adversary who manipulates ML features to evade the correct classification while minimizing or constraining the total manipulations. \textit{Problem-space} attacks refer to evasion attacks that change the actual sample. Specifically, this paper analyzes the gap between these two types in the Android malware domain. The gap between the two types of evasion attacks is examined via the retraining process of classifiers using each one of the evasion attack types. The experiments show that the gap between these two types of retrained classifiers is dramatic and may increase to 96\%. Retrained classifiers of feature-space evasion attacks have been found to be either less effective or completely ineffective against problem-space evasion attacks. Additionally, exploration of different problem-space evasion attacks shows that retraining of one problem-space evasion attack may be effective against other problem-space evasion attacks.

cs.CR↗

arXiv2022

MaMaDroid2.0 -- The Holes of Control Flow Graphs

Android malware is a continuously expanding threat to billions of mobile users around the globe. Detection systems are updated constantly to address these threats. However, a backlash takes the form of evasion attacks, in which an adversary changes malicious samples such that those samples will be misclassified as benign. This paper fully inspects a well-known Android malware detection system, MaMaDroid, which analyzes the control flow graph of the application. Changes to the portion of benign samples in the train set and models are considered to see their effect on the classifier. The changes in the ratio between benign and malicious samples have a clear effect on each one of the models, resulting in a decrease of more than 40% in their detection rate. Moreover, adopted ML models are implemented as well, including 5-NN, Decision Tree, and Adaboost. Exploration of the six models reveals a typical behavior in different cases, of tree-based models and distance-based models. Moreover, three novel attacks that manipulate the CFG and their detection rates are described for each one of the targeted models. The attacks decrease the detection rate of most of the models to 0%, with regards to different ratios of benign to malicious apps. As a result, a new version of MaMaDroid is engineered. This model fuses the CFG of the app and static analysis of features of the app. This improved model is proved to be robust against evasion attacks targeting both CFG-based models and static analysis models, achieving a detection rate of more than 90% against each one of the attacks.

cs.CR↗

arXiv2020

When the Guard failed the Droid: A case study of Android malware

Android malware is a persistent threat to billions of users around the world. As a countermeasure, Android malware detection systems are occasionally implemented. However, these systems are often vulnerable to \emph{evasion attacks}, in which an adversary manipulates malicious instances so that they are misidentified as benign. In this paper, we launch various innovative evasion attacks against several Android malware detection systems. The vulnerability inherent to all of these systems is that they are part of Androguard~\cite{desnos2011androguard}, a popular open source library used in Android malware detection systems. Some of the detection systems decrease to a 0\% detection rate after the attack. Therefore, the use of open source libraries in malware detection systems calls for caution. In addition, we present a novel evaluation scheme for evasion attack generation that exploits the weak spots of known Android malware detection systems. In so doing, we evaluate the functionality and maliciousness of the manipulated instances created by our evasion attacks. We found variations in both the maliciousness and functionality tests of our manipulated apps. We show that non-functional apps, while considered malicious, do not threaten users and are thus useless from an attacker's point of view. We conclude that evasion attacks must be assessed for both functionality and maliciousness to evaluate their impact, a step which is far from commonplace today.

cs.CR↗

arXiv2019

A wrinkle in time: A case study in DNS poisoning

The Domain Name System (DNS) provides a translation between readable domain names and IP addresses. The DNS is a key infrastructure component of the Internet and a prime target for a variety of attacks. One of the most significant threat to the DNS's wellbeing is a DNS poisoning attack, in which the DNS responses are maliciously replaced, or poisoned, by an attacker. To identify this kind of attack, we start by an analysis of different kinds of response times. We present an analysis of typical and atypical response times, while differentiating between the different levels of DNS servers' response times, from root servers down to internal caching servers. We successfully identify empirical DNS poisoning attacks based on a novel method for DNS response timing analysis. We then present a system we developed to validate our technique that does not require any changes to the DNS protocol or any existing network equipment. Our validation system tested data from different architectures including LAN and cloud environments and real data from an Internet Service Provider (ISP). Our method and system differ from most other DNS poisoning detection methods and achieved high detection rates exceeding 99%. These findings suggest that when used in conjunction with other methods, they can considerably enhance the accuracy of these methods.

cs.CR↗