Visible to the public Biblio

Filters: Keyword is insider threats  [Clear All Filters]
Ahmadi-Assalemi, Gabriela, al-Khateeb, Haider M., Epiphaniou, Gregory, Cosson, Jon, Jahankhani, Hamid, Pillai, Prashant.  2019.  Federated Blockchain-Based Tracking and Liability Attribution Framework for Employees and Cyber-Physical Objects in a Smart Workplace. 2019 IEEE 12th International Conference on Global Security, Safety and Sustainability (ICGS3). :1–9.
The systematic integration of the Internet of Things (IoT) and Cyber-Physical Systems (CPS) into the supply chain to increase operational efficiency and quality has also introduced new complexities to the threat landscape. The myriad of sensors could increase data collection capabilities for businesses to facilitate process automation aided by Artificial Intelligence (AI) but without adopting an appropriate Security-by-Design framework, threat detection and response are destined to fail. The emerging concept of Smart Workplace incorporates many CPS (e.g. Robots and Drones) to execute tasks alongside Employees both of which can be exploited as Insider Threats. We introduce and discuss forensic-readiness, liability attribution and the ability to track moving Smart SPS Objects to support modern Digital Forensics and Incident Response (DFIR) within a defence-in-depth strategy. We present a framework to facilitate the tracking of object behaviour within Smart Controlled Business Environments (SCBE) to support resilience by enabling proactive insider threat detection. Several components of the framework were piloted in a company to discuss a real-life case study and demonstrate anomaly detection and the emerging of behavioural patterns according to objects' movement with relation to their job role, workspace position and nearest entry or exit. The empirical data was collected from a Bluetooth-based Proximity Monitoring Solution. Furthermore, a key strength of the framework is a federated Blockchain (BC) model to achieve forensic-readiness by establishing a digital Chain-of-Custody (CoC) and a collaborative environment for CPS to qualify as Digital Witnesses (DW) to support post-incident investigations.
Kolokotronis, Nicholas, Brotsis, Sotirios, Germanos, Georgios, Vassilakis, Costas, Shiaeles, Stavros.  2019.  On Blockchain Architectures for Trust-Based Collaborative Intrusion Detection. 2019 IEEE World Congress on Services (SERVICES). 2642-939X:21–28.
This paper considers the use of novel technologies for mitigating attacks that aim at compromising intrusion detection systems (IDSs). Solutions based on collaborative intrusion detection networks (CIDNs) could increase the resilience against such attacks as they allow IDS nodes to gain knowledge from each other by sharing information. However, despite the vast research in this area, trust management issues still pose significant challenges and recent works investigate whether these could be addressed by relying on blockchain and related distributed ledger technologies. Towards that direction, the paper proposes the use of a trust-based blockchain in CIDNs, referred to as trust-chain, to protect the integrity of the information shared among the CIDN peers, enhance their accountability, and secure their collaboration by thwarting insider attacks. A consensus protocol is proposed for CIDNs, which is a combination of a proof-of-stake and proof-of-work protocols, to enable collaborative IDS nodes to maintain a reliable and tampered-resistant trust-chain.
Huang, Jiaju, Klee, Bryan, Schuckers, Daniel, Hou, Daqing, Schuckers, Stephanie.  2019.  Removing Personally Identifiable Information from Shared Dataset for Keystroke Authentication Research. 2019 IEEE 5th International Conference on Identity, Security, and Behavior Analysis (ISBA). :1–7.

Research on keystroke dynamics has the good potential to offer continuous authentication that complements conventional authentication methods in combating insider threats and identity theft before more harm can be done to the genuine users. Unfortunately, the large amount of data required by free-text keystroke authentication often contain personally identifiable information, or PII, and personally sensitive information, such as a user's first name and last name, username and password for an account, bank card numbers, and social security numbers. As a result, there are privacy risks associated with keystroke data that must be mitigated before they are shared with other researchers. We conduct a systematic study to remove PII's from a recent large keystroke dataset. We find substantial amounts of PII's from the dataset, including names, usernames and passwords, social security numbers, and bank card numbers, which, if leaked, may lead to various harms to the user, including personal embarrassment, blackmails, financial loss, and identity theft. We thoroughly evaluate the effectiveness of our detection program for each kind of PII. We demonstrate that our PII detection program can achieve near perfect recall at the expense of losing some useful information (lower precision). Finally, we demonstrate that the removal of PII's from the original dataset has only negligible impact on the detection error tradeoff of the free-text authentication algorithm by Gunetti and Picardi. We hope that this experience report will be useful in informing the design of privacy removal in future keystroke dynamics based user authentication systems.

Khan, Muhammad Imran, O’Sullivan, Barry, Foley, Simon N..  2018.  Towards Modelling Insiders Behaviour as Rare Behaviour to Detect Malicious RDBMS Access. 2018 IEEE International Conference on Big Data (Big Data). :3094–3099.
The heart of any enterprise is its databases where the application data is stored. Organizations frequently place certain access control mechanisms to prevent access by unauthorized employees. However, there is persistent concern about malicious insiders. Anomaly-based intrusion detection systems are known to have the potential to detect insider attacks. Accurate modelling of insiders behaviour within the framework of Relational Database Management Systems (RDBMS) requires attention. The majority of past research considers SQL queries in isolation when modelling insiders behaviour. However, a query in isolation can be safe, while a sequence of queries might result in malicious access. In this work, we consider sequences of SQL queries when modelling behaviours to detect malicious RDBMS accesses using frequent and rare item-sets mining. Preliminary results demonstrate that the proposed approach has the potential to detect malicious RDBMS accesses by insiders.
Sallam, Asmaa, Bertino, Elisa.  2018.  Detection of Temporal Data Ex-Filtration Threats to Relational Databases. 2018 IEEE 4th International Conference on Collaboration and Internet Computing (CIC). :146–155.
According to recent reports, the most common insider threats to systems are unauthorized access to or use of corporate information and exposure of sensitive data. While anomaly detection techniques have proved to be effective in the detection of early signs of data theft, these techniques are not able to detect sophisticated data misuse scenarios in which malicious insiders seek to aggregate knowledge by executing and combining the results of several queries. We thus need techniques that are able to track users' actions across time to detect correlated ones that collectively flag anomalies. In this paper, we propose such techniques for the detection of anomalous accesses to relational databases. Our approach is to monitor users' queries, sequences of queries and sessions of database connection to detect queries that retrieve amounts of data larger than the normal. Our evaluation of the proposed techniques indicates that they are very effective in the detection of anomalies.
Basu, S., Chua, Y. H. Victoria, Lee, M. Wah, Lim, W. G., Maszczyk, T., Guo, Z., Dauwels, J..  2018.  Towards a data-driven behavioral approach to prediction of insider-threat. 2018 IEEE International Conference on Big Data (Big Data). :4994–5001.

Insider threats pose a challenge to all companies and organizations. Identification of culprit after an attack is often too late and result in detrimental consequences for the organization. Majority of past research on insider threat has focused on post-hoc personality analysis of known insider threats to identify personality vulnerabilities. It has been proposed that certain personality vulnerabilities place individuals to be at risk to perpetuating insider threats should the environment and opportunity arise. To that end, this study utilizes a game-based approach to simulate a scenario of intellectual property theft and investigate behavioral and personality differences of individuals who exhibit insider-threat related behavior. Features were extracted from games, text collected through implicit and explicit measures, simultaneous facial expression recordings, and personality variables (HEXACO, Dark Triad and Entitlement Attitudes) calculated from questionnaire. We applied ensemble machine learning algorithms and show that they produce an acceptable balance of precision and recall. Our results showcase the possibility of harnessing personality variables, facial expressions and linguistic features in the modeling and prediction of insider-threat.

Shabut, A. M., Dahal, K., Kaiser, M. S., Hossain, M. A..  2017.  Malicious insider threats in tactical MANET: The performance analysis of DSR routing protocol. 2017 IEEE Region 10 Humanitarian Technology Conference (R10-HTC). :187–192.

Tactical Mobile Ad-hoc NETworks (T-MANETs) are mainly used in self-configuring automatic vehicles and robots (also called nodes) for the rescue and military operations. A high dynamic network architecture, nodes unreliability, nodes misbehavior as well as an open wireless medium make it very difficult to assume the nodes cooperation in the `ad-hoc network or comply with routing rules. The routing protocols in the T-MANET are unprotected and subsequently result in various kinds of nodes misbehavior's (such as selfishness and denial of service). This paper introduces a comprehensive analysis of the packet dropping attack includes three types of misbehavior conducted by insiders in the T-MANETs namely black hole, gray hole, and selfish behaviours. An insider threat model is appended to a state-of-the-art routing protocol (such as DSR) and analyze the effect of packet dropping attack on the performance evaluation of DSR in the T-MANET. This paper contributes to the existing knowledge in a way it allows further security research to understand the behaviours of the main threats in MANETs which depends on nods defection in the packet forwarding. The simulation of the packet dropping attack is conducted using the Network Simulator 2 (NS2). It has been found that the network throughput has dropped considerably for black and gray hole attacks whereas the selfish nodes delay the network flow. Moreover, the packet drop rate and energy consumption rate are higher for black and gray hole attacks.

Sallam, A., Bertino, E..  2017.  Detection of Temporal Insider Threats to Relational Databases. 2017 IEEE 3rd International Conference on Collaboration and Internet Computing (CIC). :406–415.

The mitigation of insider threats against databases is a challenging problem as insiders often have legitimate access privileges to sensitive data. Therefore, conventional security mechanisms, such as authentication and access control, may be insufficient for the protection of databases against insider threats and need to be complemented with techniques that support real-time detection of access anomalies. The existing real-time anomaly detection techniques consider anomalies in references to the database entities and the amounts of accessed data. However, they are unable to track the access frequencies. According to recent security reports, an increase in the access frequency by an insider is an indicator of a potential data misuse and may be the result of malicious intents for stealing or corrupting the data. In this paper, we propose techniques for tracking users' access frequencies and detecting anomalous related activities in real-time. We present detailed algorithms for constructing accurate profiles that describe the access patterns of the database users and for matching subsequent accesses by these users to the profiles. Our methods report and log mismatches as anomalies that may need further investigation. We evaluated our techniques on the OLTP-Benchmark. The results of the evaluation indicate that our techniques are very effective in the detection of anomalies.

Alzhrani, K., Rudd, E. M., Chow, C. E., Boult, T. E..  2017.  Automated U.S diplomatic cables security classification: Topic model pruning vs. classification based on clusters. 2017 IEEE International Symposium on Technologies for Homeland Security (HST). :1–6.
The U.S Government has been the target for cyberattacks from all over the world. Just recently, former President Obama accused the Russian government of the leaking emails to Wikileaks and declared that the U.S. might be forced to respond. While Russia denied involvement, it is clear that the U.S. has to take some defensive measures to protect its data infrastructure. Insider threats have been the cause of other sensitive information leaks too, including the infamous Edward Snowden incident. Most of the recent leaks were in the form of text. Due to the nature of text data, security classifications are assigned manually. In an adversarial environment, insiders can leak texts through E-mail, printers, or any untrusted channels. The optimal defense is to automatically detect the unstructured text security class and enforce the appropriate protection mechanism without degrading services or daily tasks. Unfortunately, existing Data Leak Prevention (DLP) systems are not well suited for detecting unstructured texts. In this paper, we compare two recent approaches in the literature for text security classification, evaluating them on actual sensitive text data from the WikiLeaks dataset.
Bhattacharjee, S. Das, Yuan, J., Jiaqi, Z., Tan, Y. P..  2017.  Context-aware graph-based analysis for detecting anomalous activities. 2017 IEEE International Conference on Multimedia and Expo (ICME). :1021–1026.

This paper proposes a context-aware, graph-based approach for identifying anomalous user activities via user profile analysis, which obtains a group of users maximally similar among themselves as well as to the query during test time. The main challenges for the anomaly detection task are: (1) rare occurrences of anomalies making it difficult for exhaustive identification with reasonable false-alarm rate, and (2) continuously evolving new context-dependent anomaly types making it difficult to synthesize the activities apriori. Our proposed query-adaptive graph-based optimization approach, solvable using maximum flow algorithm, is designed to fully utilize both mutual similarities among the user models and their respective similarities with the query to shortlist the user profiles for a more reliable aggregated detection. Each user activity is represented using inputs from several multi-modal resources, which helps to localize anomalies from time-dependent data efficiently. Experiments on public datasets of insider threats and gesture recognition show impressive results.

Reinerman-Jones, L., Matthews, G., Wohleber, R., Ortiz, E..  2017.  Scenarios using situation awareness in a simulation environment for eliciting insider threat behavior. 2017 IEEE Conference on Cognitive and Computational Aspects of Situation Management (CogSIMA). :1–3.

An important topic in cybersecurity is validating Active Indicators (AI), which are stimuli that can be implemented in systems to trigger responses from individuals who might or might not be Insider Threats (ITs). The way in which a person responds to the AI is being validated for identifying a potential threat and a non-threat. In order to execute this validation process, it is important to create a paradigm that allows manipulation of AIs for measuring response. The scenarios are posed in a manner that require participants to be situationally aware that they are being monitored and have to act deceptively. In particular, manipulations in the environment should no differences between conditions relative to immersion and ease of use, but the narrative should be the driving force behind non-deceptive and IT responses. The success of the narrative and the simulation environment to induce such behaviors is determined by immersion, usability, and stress response questionnaires, and performance. Initial results of the feasibility to use a narrative reliant upon situation awareness of monitoring and evasion are discussed.

Ogiela, L., Ogiela, M. R..  2017.  Insider Threats and Cryptographic Techniques in Secure Information Management. IEEE Systems Journal. 11:405–414.

This publication presents some techniques for insider threats and cryptographic protocols in secure processes. Those processes are dedicated to the information management of strategic data splitting. Strategic data splitting is dedicated to enterprise management processes as well as methods of securely storing and managing this type of data. Because usually strategic data are not enough secure and resistant for unauthorized leakage, we propose a new protocol that allows to protect data in different management structures. The presented data splitting techniques will concern cryptographic information splitting algorithms, as well as data sharing algorithms making use of cognitive data analysis techniques. The insider threats techniques will concern data reconstruction methods and cognitive data analysis techniques. Systems for the semantic analysis and secure information management will be used to conceal strategic information about the condition of the enterprise. Using the new approach, which is based on cognitive systems allow to guarantee the secure features and make the management processes more efficient.

Santos, E. E., Santos, E., Korah, J., Thompson, J. E., Murugappan, V., Subramanian, S., Zhao, Yan.  2017.  Modeling insider threat types in cyber organizations. 2017 IEEE International Symposium on Technologies for Homeland Security (HST). :1–7.

Insider threats can cause immense damage to organizations of different types, including government, corporate, and non-profit organizations. Being an insider, however, does not necessarily equate to being a threat. Effectively identifying valid threats, and assessing the type of threat an insider presents, remain difficult challenges. In this work, we propose a novel breakdown of eight insider threat types, identified by using three insider traits: predictability, susceptibility, and awareness. In addition to presenting this framework for insider threat types, we implement a computational model to demonstrate the viability of our framework with synthetic scenarios devised after reviewing real world insider threat case studies. The results yield useful insights into how further investigation might proceed to reveal how best to gauge predictability, susceptibility, and awareness, and precisely how they relate to the eight insider types.

Legg, P. A., Buckley, O., Goldsmith, M., Creese, S..  2017.  Automated Insider Threat Detection System Using User and Role-Based Profile Assessment. IEEE Systems Journal. 11:503–512.

Organizations are experiencing an ever-growing concern of how to identify and defend against insider threats. Those who have authorized access to sensitive organizational data are placed in a position of power that could well be abused and could cause significant damage to an organization. This could range from financial theft and intellectual property theft to the destruction of property and business reputation. Traditional intrusion detection systems are neither designed nor capable of identifying those who act maliciously within an organization. In this paper, we describe an automated system that is capable of detecting insider threats within an organization. We define a tree-structure profiling approach that incorporates the details of activities conducted by each user and each job role and then use this to obtain a consistent representation of features that provide a rich description of the user's behavior. Deviation can be assessed based on the amount of variance that each user exhibits across multiple attributes, compared against their peers. We have performed experimentation using ten synthetic data-driven scenarios and found that the system can identify anomalous behavior that may be indicative of a potential threat. We also show how our detection system can be combined with visual analytics tools to support further investigation by an analyst.

Almehmadi, A., El-khatib, K..  2017.  On the Possibility of Insider Threat Prevention Using Intent-Based Access Control (IBAC). IEEE Systems Journal. 11:373–384.

Existing access control mechanisms are based on the concept of identity enrolment and recognition and assume that recognized identity is a synonym to ethical actions, yet statistics over the years show that the most severe security breaches are the results of trusted, identified, and legitimate users who turned into malicious insiders. Insider threat damages vary from intellectual property loss and fraud to information technology sabotage. As insider threat incidents evolve, there exist demands for a nonidentity-based authentication measure that rejects access to authorized individuals who have mal-intents of access. In this paper, we study the possibility of using the user's intention as an access control measure using the involuntary electroencephalogram reactions toward visual stimuli. We propose intent-based access control (IBAC) that detects the intentions of access based on the existence of knowledge about an intention. IBAC takes advantage of the robustness of the concealed information test to assess access risk. We use the intent and intent motivation level to compute the access risk. Based on the calculated risk and risk accepted threshold, the system makes the decision whether to grant or deny access requests. We assessed the model using experiments on 30 participants that proved the robustness of the proposed solution.

Feng, W., Yan, W., Wu, S., Liu, N..  2017.  Wavelet transform and unsupervised machine learning to detect insider threat on cloud file-sharing. 2017 IEEE International Conference on Intelligence and Security Informatics (ISI). :155–157.

As increasingly more enterprises are deploying cloud file-sharing services, this adds a new channel for potential insider threats to company data and IPs. In this paper, we introduce a two-stage machine learning system to detect anomalies. In the first stage, we project the access logs of cloud file-sharing services onto relationship graphs and use three complementary graph-based unsupervised learning methods: OddBall, PageRank and Local Outlier Factor (LOF) to generate outlier indicators. In the second stage, we ensemble the outlier indicators and introduce the discrete wavelet transform (DWT) method, and propose a procedure to use wavelet coefficients with the Haar wavelet function to identify outliers for insider threat. The proposed system has been deployed in a real business environment, and demonstrated effectiveness by selected case studies.

Gamachchi, A., Boztas, S..  2017.  Insider Threat Detection Through Attributed Graph Clustering. 2017 IEEE Trustcom/BigDataSE/ICESS. :112–119.

While most organizations continue to invest in traditional network defences, a formidable security challenge has been brewing within their own boundaries. Malicious insiders with privileged access in the guise of a trusted source have carried out many attacks causing far reaching damage to financial stability, national security and brand reputation for both public and private sector organizations. Growing exposure and impact of the whistleblower community and concerns about job security with changing organizational dynamics has further aggravated this situation. The unpredictability of malicious attackers, as well as the complexity of malicious actions, necessitates the careful analysis of network, system and user parameters correlated with insider threat problem. Thus it creates a high dimensional, heterogeneous data analysis problem in isolating suspicious users. This research work proposes an insider threat detection framework, which utilizes the attributed graph clustering techniques and outlier ranking mechanism for enterprise users. Empirical results also confirm the effectiveness of the method by achieving the best area under curve value of 0.7648 for the receiver operating characteristic curve.

Zaytsev, A., Malyuk, A., Miloslavskaya, N..  2017.  Critical Analysis in the Research Area of Insider Threats. 2017 IEEE 5th International Conference on Future Internet of Things and Cloud (FiCloud). :288–296.

The survey of related works on insider information security (IS) threats is presented. Special attention is paid to works that consider the insiders' behavioral models as it is very up-to-date for behavioral intrusion detection. Three key research directions are defined: 1) the problem analysis in general, including the development of taxonomy for insiders, attacks and countermeasures; 2) study of a specific IS threat with forecasting model development; 3) early detection of a potential insider. The models for the second and third directions are analyzed in detail. Among the second group the works on three IS threats are examined, namely insider espionage, cyber sabotage and unintentional internal IS violation. Discussion and a few directions for the future research conclude the paper.

Lin, L., Zhong, S., Jia, C., Chen, K..  2017.  Insider Threat Detection Based on Deep Belief Network Feature Representation. 2017 International Conference on Green Informatics (ICGI). :54–59.

Insider threat is a significant security risk for information system, and detection of insider threat is a major concern for information system organizers. Recently existing work mainly focused on the single pattern analysis of user single-domain behavior, which were not suitable for user behavior pattern analysis in multi-domain scenarios. However, the fusion of multi-domain irrelevant features may hide the existence of anomalies. Previous feature learning methods have relatively a large proportion of information loss in feature extraction. Therefore, this paper proposes a hybrid model based on the deep belief network (DBN) to detect insider threat. First, an unsupervised DBN is used to extract hidden features from the multi-domain feature extracted by the audit logs. Secondly, a One-Class SVM (OCSVM) is trained from the features learned by the DBN. The experimental results on the CERT dataset demonstrate that the DBN can be used to identify the insider threat events and it provides a new idea to feature processing for the insider threat detection.

Agrafiotis, Ioannis, Erola, Arnau, Goldsmith, Michael, Creese, Sadie.  2016.  A Tripwire Grammar for Insider Threat Detection. Proceedings of the 8th ACM CCS International Workshop on Managing Insider Security Threats. :105–108.

The threat from insiders is an ever-growing concern for organisations, and in recent years the harm that insiders pose has been widely demonstrated. This paper describes our recent work into how we might support insider threat detection when actions are taken which can be immediately determined as of concern because they fall into one of two categories: they violate a policy which is specifically crafted to describe behaviours that are highly likely to be of concern if they are exhibited, or they exhibit behaviours which follow a pattern of a known insider threat attack. In particular, we view these concerning actions as something that we can design and implement tripwires within a system to detect. We then orchestrate these tripwires in conjunction with an anomaly detection system and present an approach to formalising tripwires of both categories. Our intention being that by having a single framework for describing them, alongside a library of existing tripwires in use, we can provide the community of practitioners and researchers with the basis to document and evolve this common understanding of tripwires.

Sanzgiri, Ameya, Dasgupta, Dipankar.  2016.  Classification of Insider Threat Detection Techniques. Proceedings of the 11th Annual Cyber and Information Security Research Conference. :25:1–25:4.

Most insider attacks done by people who have the knowledge and technical know-how of launching such attacks. This topic has long been studied and many detection techniques were proposed to deal with insider threats. This short paper summarized and classified insider threat detection techniques based on strategies used for detection.

Wiese, Oliver, Roth, Volker.  2016.  See You Next Time: A Model for Modern Shoulder Surfers. Proceedings of the 18th International Conference on Human-Computer Interaction with Mobile Devices and Services. :453–464.

Friends, family and colleagues at work may repeatedly observe how their peers unlock their smartphones. These "insiders" may combine multiple partial observations to form a hypothesis of a target's secret. This changing landscape requires that we update the methods used to assess the security of unlocking mechanisms against human shoulder surfing attacks. In our paper, we introduce a methodology to study shoulder surfing risks in the insider threat model. Our methodology dissects the authentication process into minimal observations by humans. Further processing is based on simulations. The outcome is an estimate of the number of observations needed to break a mechanism. The flexibility of this approach benefits the design of new mechanisms. We demonstrate the application of our methodology by performing an analysis of the SwiPIN scheme published at CHI 2015. Our results indicate that SwiPIN can be defeated reliably by a majority of the population with as few as 6 to 11 observations.

Shalev, Noam, Keidar, Idit, Moatti, Yosef, Weinsberg, Yaron.  2016.  WatchIT: Who Watches Your IT Guy? Proceedings of the 8th ACM CCS International Workshop on Managing Insider Security Threats. :93–96.

System administrators have unlimited access to system resources. As the Snowden case shows, these permissions can be exploited to steal valuable personal, classified, or commercial data. In this work we propose a strategy that increases the organizational information security by constraining IT personnel's view of the system and monitoring their actions. To this end, we introduce the abstraction of perforated containers – while regular Linux containers are too restrictive to be used by system administrators, by "punching holes" in them, we strike a balance between information security and required administrative needs. Our system predicts which system resources should be accessible for handling each IT issue, creates a perforated container with the corresponding isolation, and deploys it in the corresponding machines as needed for fixing the problem. Under this approach, the system administrator retains his superuser privileges, while he can only operate within the container limits. We further provide means for the administrator to bypass the isolation, and perform operations beyond her boundaries. However, such operations are monitored and logged for later analysis and anomaly detection. We provide a proof-of-concept implementation of our strategy, along with a case study on the IT database of IBM Research in Israel.

X. Feng, Z. Zheng, P. Hu, D. Cansever, P. Mohapatra.  2015.  "Stealthy attacks meets insider threats: A three-player game model". MILCOM 2015 - 2015 IEEE Military Communications Conference. :25-30.

Advanced persistent threat (APT) is becoming a major threat to cyber security. As APT attacks are often launched by well funded entities that are persistent and stealthy in achieving their goals, they are highly challenging to combat in a cost-effective way. The situation becomes even worse when a sophisticated attacker is further assisted by an insider with privileged access to the inside information. Although stealthy attacks and insider threats have been considered separately in previous works, the coupling of the two is not well understood. As both types of threats are incentive driven, game theory provides a proper tool to understand the fundamental tradeoffs involved. In this paper, we propose the first three-player attacker-defender-insider game to model the strategic interactions among the three parties. Our game extends the two-player FlipIt game model for stealthy takeover by introducing an insider that can trade information to the attacker for a profit. We characterize the subgame perfect equilibria of the game with the defender as the leader and the attacker and the insider as the followers, under two different information trading processes. We make various observations and discuss approaches for achieving more efficient defense in the face of both APT and insider threats.