Misuse or malicious access to critical assets of information systems by insiders usually causes significant loss to organizations. The issue of insider threat detection for information systems has received many researchers’ attention in both security and data mining fields, and a lot of related research results were presented. However, there are still many challenges in capturing the behavior difference between malicious insiders and normal users accurately, such as lack of labeled insider threats, the subtle and adaptive nature of insider threats, complexity, heterogeneity, sparsity of the underlying data, etc. To detect insider threats with large and complex audit data, a Multi-Edge Weight Relational Graph Neural Network method (MEWRGNN) for robust anomaly detection is proposed in this paper. Unlike most existing approaches, the MEWRGNN adopts several graph neural networks to capture the contextual relationship of user behaviors over a period of time, which is a critical factor for achieving accurate anomaly identification. The MEWRGNN achieves a certain degree of interpretability through ranking the contribution of different edge-representation features. Evaluation experimental results demonstrate that the MEWRGNN can learn a model from limited sample data sets, and achieve quick and accurate insider threat detection performance. In addition, other feature ranking results allow providing security analysts with understandable insights for investigating the detected insider threats.

Anomaly detection for discrete event logs can provide critical information for building secure and reliable systems in various application domains, such as large scale data centers, autonomous driving, and intrusion detection. However, the task is very challenging due to the lack of a clear understanding and definition of anomaly in the specific problem space, and the log data is often highly complex with temporal correlation. Existing deep learning based methods mostly suffer from such issues as overfitting, uncertainty or low interpretability; consequently, the detection results may be inaccurate, with little information to help security analysts diagnose the reported anomalies with high confidence. To tackle this challenge, in this research, we propose a general framework named MADDC, which aims to (1) accurately perform Multi-scale Anomaly Detection, Diagnosis and Correction for discrete event logs, and (2) help analysts further mitigate anomalies based on diagnosis results. Specifically, we first design a new anomaly critic for LSTM variational autoencoder based model to alleviate overfitting and reduce false negatives during anomaly detection. As one of our main contributions, we then introduce process mining technique to build process-centric workflow models in an unsupervised manner, which forms the ‘normal’ context of an event sequence and help perform accurate and consistent anomaly diagnosis through global sequence alignment. Experiments on publicly available datasets show that MADDC not only outperformed several representative methods in terms of detection accuracy, but also could improve the visibility to abnormal deviations from normal execution, hence helping security analysts understand anomalies and make further corrections.

Insider threat detection has been a challenging task over decades; existing approaches generally employ the traditional generative unsupervised learning methods to produce normal user behavior model and detect significant deviations as anomalies. However, such approaches are insufficient in precision and computational complexity. In this paper, we propose a novel insider threat detection method, Image-based Insider Threat Detector via Geometric Transformation (IGT), which converts the unsupervised anomaly detection into supervised image classification task, and therefore the performance can be boosted via computer vision techniques. To illustrate, our IGT uses a novel image-based feature representation of user behavior by transforming audit logs into grayscale images. By applying multiple geometric transformations on these behavior grayscale images, IGT constructs a self-labelled dataset and then trains a behavior classifier to detect anomaly in a self-supervised manner. The motivation behind our proposed method is that images converted from normal behavior data may contain unique latent features which remain unchanged after geometric transformation, while malicious ones cannot. Experimental results on CERT dataset show that IGT outperforms the classical autoencoder-based unsupervised insider threat detection approaches, and improves the instance and user based Area under the Receiver Operating Characteristic Curve (AUROC) by 4% and 2%, respectively.

Serious concerns have been raised about user's privacy leak in mobile apps, and many detection approaches are proposed. To evade detection, new mobile malware starts to mimic privacy-related behaviours of benign apps, and mix malicious privacy leak with benign ones to reduce the chance of being observed. Since prior proposed approaches primarily focus on the privacy leak discovery, these evasive techniques will make differentiating between malicious and benign privacy disclosures difficult during privacy leak analysis. In this paper, we propose PrivacyContext to identify malicious privacy leak using context. PrivacyContext can be used to purify privacy leak detection results for automatic and easy interpretation by filtering benign privacy disclosures. Experiments show PrivacyContext can perform an effective and efficient static privacy disclosure analysis enhancement and identify malicious privacy leak with 92.73% true positive rate. Evaluation also indicates that to keep the accuracy of privacy disclosure classification, our proposed contexts are all necessary.

Automatically triggering malicious behaviors is an essential step to understand malware for developing effective solutions. Existing automated dynamic analysis approaches usually try to trigger the malicious behaviors by relying on simple fuzzing or complex input generation techniques (e.g., concolic execution). However, advanced malware often adopt various evasion techniques to hide malicious behaviors, e.g., by introducing complex condition checks which are very hard to trigger. In this paper, we propose a new approach named DirectDroid, which bypasses related checks through on-demand forced execution while adopting fuzzingto feed the necessary program input. In this way, many hidden malicious behaviors can be successfully triggered. To ensure the normal execution towards the malicious behaviors, DirectDroid also largely handles potential program crashes caused by forced execution. Finally, we implement a prototype of DirectDroid and evaluate it against 951 recent malware samples. Our experiment results show that DirectDroid can trigger many more malicious behaviors than several previous works, even when crashes happened. Our further analysis shows that DirectDroid has a low false positive rate even though it adopts forced execution.

While many test input generation techniques have been proposed to improve the code coverage of dynamic analysis, they are still inefficient in triggering hidden malicious behaviors protected by anti-analysis techniques. In this work, we design and implement Droid-AntiRM, a new approach seeking to tame anti-analysis automatically and improve automated dynamic analysis. Our approach leverages three key observations: 1) Logic-bomb based anti-analysis techniques control the execution of certain malicious behaviors; 2) Anti-analysis techniques are normally implemented through condition statements; 3) Anti-analysis techniques normally have no dependence on program inputs. Based on these observations, Droid-AntiRM uses various techniques to detect anti-analysis in malware samples, and rewrite the condition statements in anti-analysis cases through bytecode instrumentation, thus forcing the hidden behavior to be executed at runtime. Through a study of 3187 malware samples, we find that 32.50% of them employ various anti-analysis techniques. Our experiments demonstrate that Droid-AntiRM can identify anti-analysis instances from 30 malware samples with a true positive rate of 89.15% and zero false negative. By taming the identified anti-analysis, Droid-AntiRM can greatly improve the automated dynamic analysis, successfully triggering 44 additional hidden malicious behaviors from the 30 samples. Further performance evaluation shows that Droid-AntiRM has good efficiency to perform large-scale analysis.

Peer-to-Peer (P2P) traffic has always been a dominant portion of current Internet traffic and become more and more difficult to manage for Internet Service Producers (ISP) and network administrators. Although many methods have been proposed to classify different types of P2P applications and achieved satisfied performance, research on identifying network activities of a certain P2P application is still lacking to the best of our knowledge, which is urgently required in the context of forensic investigation for illegal P2P applications. In this paper, a novel approach based on Hidden Markov Model is proposed to identify network activities on the encrypted traffic, based on analysis of the time series characteristics and statistical properties of network traffic. After presenting a general model of network activities, Team Viewer is selected as a case study to verify the effectiveness of the approach to identify different activities. According to experiments using real network traces, our approach proves to be effective in identifying different activities of a P2P application with a high true positive 99.1% and low negligible false positive 3.6%.