Ondřej Lukas

Graph Generative Models for Decoy Targets in Active Directory

Graph Generative Models for Decoy Targets in Active Directory

Active Directory (AD) is a crucial element of large organizations, given its central role in managing access to resources. However, since AD is used by all users in the organization, it is hard to detect attackers. We propose to generate and place fake users (honeyusers) in AD structures to help detect attacks. However, not any honeyuser will attract attackers. Our method generates honeyusers with a Variational Autoencoder that enriches the AD structure with well-positioned honeyusers. Our model first learns the embeddings of the original nodes and edges in the AD, then it uses a modified Bidirectional DAG-RNN to encode the parameters of the probability distribution of the latent space of node representations. Finally, it samples nodes from this distribution and uses an MLP to decide where the nodes are connected. The model was first evaluated by the similarity of the generated AD with the original AD, second by the positions of the new nodes, and finally making real intruders attack the AD structure enriched with honeyusers to see if they selected the honeyusers. Results show that our machine learning model is good enough to generate well-placed honeyusers for existing AD structures so that intruders are lured into them.

IDENTIFYING MALICIOUS HOSTS BY AGGREGATION OF PARTIAL DETECTIONS

Bachelor Thesis

This thesis proposes to design, implement and test a machine learning improvement of Stratosphere IPS which aggregates the partial detections of hosts and classifies them using the XGBoost algorithm to improve the overall performance of the tool. Our method is based on an additional layer of abstraction called Source Address layer which collects the partial data and pre-processes it or the classifier. Compared to the first version of Stratosphere IPS proposed extension results in 40% increase in accuracy and 26% improvement in the False Positive rate.