Biblio

Advanced Persistent Threats (APT) consist of most skillful hackers who employ sophisticated techniques to stealthily gain unauthorized access to private networks and exfiltrate sensitive data. When their existence is discovered, organizations - if they can sustain business continuity - mostly have to perform forensics activities to assess the damage of the attack and discover the extent of sensitive data leakage. In this paper, we construct a novel framework to pinpoint sensitive data that may have been leaked in such an attack. Our framework consists of creating baseline fingerprints for each workstation for setting normal activity, and we consider the change in the behavior of the network overall. We compare the accused fingerprint with sensitive database information by utilizing both Levenstein distance and TF-IDF/cosine similarity resulting in a similarity percentage. This allows us to pinpoint what part of data was exfiltrated by the perpetrators, where in the network the data originated, and if that data is sensitive to the private company's network. We then perform feasibility experiments to show that even these simple methods are feasible to run on a network representative of a mid-size business.

Insider attacks are one of the most dangerous threats to an organization. Unfortunately, they are very difficult to foresee, detect, and defend against due to the trust and responsibilities placed on the employees. In this paper, we first define the notion of user intent, and construct a model for the most common threat scenario used in the literature that poses a very high risk for sensitive data stored in the organization's database. We show that the complexity of identifying pseudo-intents of a user is coNP-Complete in this domain, and launching a harvester insider attack within the boundaries of the defined threat model takes linear time while a targeted threat model is an NP-Complete problem. We also discuss about the general defense mechanisms against the modeled threats, and show that countering against the harvester insider attack model takes quadratic time while countering against the targeted insider attack model can take linear to quadratic time depending on the strategy chosen. Finally, we analyze the adversarial behavior, and show that launching an attack with minimum risk is also an NP-Complete problem.