Towards Automatic Hands-on-Keyboard Attack Detection Using LLMs in EDR Solutions

Endpoint Detection and Remediation (EDR) platforms are essential for identifying and responding to cyber threats. This study presents a novel approach using Large Language Models (LLMs) to detect Hands-on-Keyboard (HOK) cyberattacks. Our method involves converting endpoint activity data into narrative forms that LLMs can analyze to distinguish between normal operations and potential HOK attacks. We address the challenges of interpreting endpoint data by segmenting narratives into windows and employing a dual training strategy. The results demonstrate that LLM-based models have the potential to outperform traditional machine learning methods, offering a promising direction for enhancing EDR capabilities and apply LLMs in cybersecurity.

Detecting Malicious PowerShell Scripts Using Contextual Embeddings

PowerShell is a command line shell, that is widely used in organizations for configuration management and task automation. Unfortunately, PowerShell is also increasingly used by cybercriminals for launching cyber attacks against organizations, mainly because it is pre-installed on Windows machines and it exposes strong functionality that may be leveraged by attackers. This makes the problem of detecting malicious PowerShell scripts both urgent and challenging. We address this important problem by presenting several novel deep learning based detectors of malicious PowerShell scripts. Our best model obtains a true positive rate of nearly 90% while maintaining a low false positive rate of less than 0.1%, indicating that it can be of practical value. Our models employ pre-trained contextual embeddings of words from the PowerShell "language". A contextual word embedding is able to project semantically similar words to proximate vectors in the embedding space. A known problem in the cybersecurity domain is that labeled data is relatively scarce in comparison with unlabeled data, making it difficult to devise effective supervised detection of malicious activity of many types. This is also the case with PowerShell scripts. Our work shows that this problem can be largely mitigated by learning a pre-trained contextual embedding based on unlabeled data. We trained our models' embedding layer using a scripts dataset that was enriched by a large corpus of unlabeled PowerShell scripts collected from public repositories. As established by our performance analysis, the use of unlabeled data for the embedding significantly improved the performance of our detectors. We estimate that the usage of pre-trained contextual embeddings based on unlabeled data for improved classification accuracy will find additional applications in the cybersecurity domain.

Detecting Malicious PowerShell Commands using Deep Neural Networks

Microsoft's PowerShell is a command-line shell and scripting language that is installed by default on Windows machines. While PowerShell can be configured by administrators for restricting access and reducing vulnerabilities, these restrictions can be bypassed. Moreover, PowerShell commands can be easily generated dynamically, executed from memory, encoded and obfuscated, thus making the logging and forensic analysis of code executed by PowerShell challenging.For all these reasons, PowerShell is increasingly used by cybercriminals as part of their attacks' tool chain, mainly for downloading malicious contents and for lateral movement. Indeed, a recent comprehensive technical report by Symantec dedicated to PowerShell's abuse by cybercrimials reported on a sharp increase in the number of malicious PowerShell samples they received and in the number of penetration tools and frameworks that use PowerShell. This highlights the urgent need of developing effective methods for detecting malicious PowerShell commands.In this work, we address this challenge by implementing several novel detectors of malicious PowerShell commands and evaluating their performance. We implemented both "traditional" natural language processing (NLP) based detectors and detectors based on character-level convolutional neural networks (CNNs). Detectors' performance was evaluated using a large real-world dataset.Our evaluation results show that, although our detectors individually yield high performance, an ensemble detector that combines an NLP-based classifier with a CNN-based classifier provides the best performance, since the latter classifier is able to detect malicious commands that succeed in evading the former. Our analysis of these evasive commands reveals that some obfuscation patterns automatically detected by the CNN classifier are intrinsically difficult to detect using the NLP techniques we applied.