Sameera Horawalavithana

Sameera Horawalavithana

Seattle, Washington, United States
2K followers 500+ connections

About

I am a Staff Scientist at Pacific Northwest National Laboratory. I received my Ph.D. in…

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Experience

  • Pacific Northwest National Laboratory Graphic

    Pacific Northwest National Laboratory

    Seattle, Washington, United States

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    Richland, Washington, United States

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    Tampa/St. Petersburg, Florida Area

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    Department of Computer Science and Engineering

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    Colombo, Western, Sri Lanka

Education

  • University of South Florida Graphic
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    Activities and Societies: Mentoring student projects, SCORE research lab

    BSc (Hons.) in Computer Science

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    Activities and Societies: International Buddy Program

    Exchange Student

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    Activities and Societies: Junior Entrepreneurship Society

Licenses & Certifications

Volunteer Experience

Publications

  • Twitter is the Megaphone of Cross-Platform Messaging on the White Helmets

    International Conference on Social Computing, Behavioral-Cultural Modeling, & Prediction and Behavior Representation in Modeling and Simulation

    This work provides a quantitative analysis of the cross-platform disinformation campaign on Twitter against the Syrian Civil Defence group known as the White Helmets. Based on four months of Twitter messages, this article analyzes the promotion of urls from different websites, such as alternative media, YouTube, and other social media platforms. Our study shows that alternative media urls and YouTube videos are heavily promoted together; fact-checkers and official government sites are rarely…

    This work provides a quantitative analysis of the cross-platform disinformation campaign on Twitter against the Syrian Civil Defence group known as the White Helmets. Based on four months of Twitter messages, this article analyzes the promotion of urls from different websites, such as alternative media, YouTube, and other social media platforms. Our study shows that alternative media urls and YouTube videos are heavily promoted together; fact-checkers and official government sites are rarely mentioned; and there are clear signs of a coordinated campaign manifested through repeated messaging from the same user accounts.

    See publication
  • Mentions of Security Vulnerabilities in Reddit, Twitter and GitHub,

    IEEE/WIC/ACM International Conference on Web Intelligence

    Activity on social media is seen as a relevant sensor for different aspects of the society. In a heavily digitized society, security vulnerabilities pose a significant threat that is publicly discussed on social media. This study presents a comparison of user-generated content related to security vulnerabilities on three digital platforms: two social media conversation channels (Reddit and Twitter) and a collaborative software development platform (GitHub). Our data analysis shows that while…

    Activity on social media is seen as a relevant sensor for different aspects of the society. In a heavily digitized society, security vulnerabilities pose a significant threat that is publicly discussed on social media. This study presents a comparison of user-generated content related to security vulnerabilities on three digital platforms: two social media conversation channels (Reddit and Twitter) and a collaborative software development platform (GitHub). Our data analysis shows that while more security vulnerabilities are discussed on Twitter, relevant conversations go viral earlier on Reddit. We show that the two social media platforms can be used to accurately predict activity on GitHub.

    See publication
  • Behind the Mask: Understanding the Structural Forces that Make Social Graphs Vulnerable to De-anonymization.

    IEEE Transactions on Computational Social Systems (TCSS)

    The tradeoff between anonymity and utility in the context of the anonymization of graph data sets is well acknowledged; for better privacy, some of the graph structural properties must be lost. What is not well understood, however, is what forces shape this tradeoff. Specifically, for the data practitioner who wants to publish an anonymized graph data set, it is unclear what graph structural properties can be preserved and what are the anonymity costs associated with preserving them. This…

    The tradeoff between anonymity and utility in the context of the anonymization of graph data sets is well acknowledged; for better privacy, some of the graph structural properties must be lost. What is not well understood, however, is what forces shape this tradeoff. Specifically, for the data practitioner who wants to publish an anonymized graph data set, it is unclear what graph structural properties can be preserved and what are the anonymity costs associated with preserving them. This article proposes a framework that examines the interplay between graph properties and the vulnerability to deanonymization attacks. We demonstrate its applicability via extensive experiments on thousands of graphs with controlled properties generated from real data sets. In addition, we show empirically that there are structural properties that affect graph vulnerability to reidentification attacks independent of degree distribution.

    See publication
  • Diversity, Topology, and the Risk of Node Re-identification in Labeled Social Graphs.

    The 7th International Conference on Complex Networks and Their Applications (Complex Networks)

    Real network datasets provide significant benefits for understanding phenomena such as information diffusion or network evolution. Yet the privacy risks raised from sharing real graph datasets, even when
    stripped of user identity information, are significant. When nodes have associated attributes, the privacy risks increase. In this paper we quantitatively study the impact of binary node attributes on node privacy by employing machine-learning-based re-identification attacks and exploring…

    Real network datasets provide significant benefits for understanding phenomena such as information diffusion or network evolution. Yet the privacy risks raised from sharing real graph datasets, even when
    stripped of user identity information, are significant. When nodes have associated attributes, the privacy risks increase. In this paper we quantitatively study the impact of binary node attributes on node privacy by employing machine-learning-based re-identification attacks and exploring the interplay between graph topology and attribute placement. Our experiments show that the population’s diversity on the binary attribute consistently degrades anonymity

    See publication
  • An Efficient Incremental Indexing Mechanism for Extracting Top-k Representative Queries Over Continuous Data-streams

    ACM/IFIP/USENIX Middleware 2015

    Top-k publish/subscribe (pub/sub) models have gained traction as an expressive alternative to extend the binary notion of matching. In our study, we focus on the problem of extracting the k-most representative set of publications in the dynamic case where the results are updated over a
    stream of matching publications. This can be observed as the minimum independent dominating set problem in graph theory, when streaming publications are represented as dynamic graph spaces. Due to the inherent…

    Top-k publish/subscribe (pub/sub) models have gained traction as an expressive alternative to extend the binary notion of matching. In our study, we focus on the problem of extracting the k-most representative set of publications in the dynamic case where the results are updated over a
    stream of matching publications. This can be observed as the minimum independent dominating set problem in graph theory, when streaming publications are represented as dynamic graph spaces. Due to the inherent complexity of solving this problem over continuous data, an incremental
    indexing mechanism is proposed for handling a stream of publications. The proposed mechanism is based on Locality Sensitive Hashing (LSH) to avoid the overhead of recalculating neighborhoods over consecutive sliding windows. The experimental results show that the incremental version of
    LSH indexing mechanism reduces the computational cost of naive greedy approach significantly, while producing Top-k representative results at 70% accuracy compared to the naive optimal method.

    Other authors
    • D.N.Ranasinghe
    See publication

Courses

  • Artificial Intelligence Methods & Applications

    5DV058

  • Compilers and Automata Theory

    SCS3008

  • Computational Pattern Recognition

    SCS4019

  • Computer System Architecture

    SCS3013

  • Cryptography Systems

    SCS3011

  • Data Mining

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  • Deep Learning

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  • Distributed Systems

    5DV147

  • Fundamentals of Artificial Intelligence

    5DV121

  • Graph Data Processing

    CIS6930

  • High Performance Computing

    SCS4007

  • Introduction to Theory of Algorithms

    COT6405

  • Middleware Architectures

    SCS3009

  • Networking Technologies

    SCS3004

  • Operating Systems

    COP6611

  • Principles of Computer Architecture

    EEL6764

  • Social Network Analysis

    SYA7357

  • Special Topics in Theoritical Computing

    SCS4009

  • System Security

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  • Wireless Ad-Hoc and Sensor Networks (WASN)

    SCS4017

Projects

  • Modeling Information Diffusion Processes with Deep Learning Algorithms (SocialSim)

    - Present

    The principal research objective of the project is to evaluate deep learning methodologies using neural networks for predicting information diffusion processes in various social online environments. While deep learning has been shown to be a valuable tool in recognizing images, it has not been sufficiently explored in the context of dynamic processes on social networks. Yet, we believe, with the right techniques in place, deep learning can contribute significantly to predicting dynamic…

    The principal research objective of the project is to evaluate deep learning methodologies using neural networks for predicting information diffusion processes in various social online environments. While deep learning has been shown to be a valuable tool in recognizing images, it has not been sufficiently explored in the context of dynamic processes on social networks. Yet, we believe, with the right techniques in place, deep learning can contribute significantly to predicting dynamic processes on social networks at scale.

    In our first phase, we used Long Short Term Memory (LSTM) neural network to model information cascades. We proposed a graph-representational learning framework (aka Cascade-LSTM), and simulate information cascades around communities of popular crypto-currency systems appeared Reddit, Github and Twitter. The crypto-currency systems are highly volatile and evolve quickly. Also, cryptocurrencies are disproportionately used by criminals and hackers, and their use has political and economic implications for the U.S. Thus, understanding, explaining, and anticipating the social behavior and communication patterns in the social environments surrounding cryptocurrencies is crucial to understand this phenomena and devise appropriate responses.

    See project
  • Structural Anonymization Techniques for Large, Labeled, and Dynamic Social Graphs

    - Present

    The objective of this work is to provide big data owners with tools to safely share their social networks data with the research community. The project aims to approach graph anonymization via two techniques for graph generation: dK-series techniques, introduced in the context of internet network generation, and Exponential Random Graph Model-based approaches (ERGM). My contribution is related to privacy/ utility measures, and how such graph annonymization techniques could apply on evolving…

    The objective of this work is to provide big data owners with tools to safely share their social networks data with the research community. The project aims to approach graph anonymization via two techniques for graph generation: dK-series techniques, introduced in the context of internet network generation, and Exponential Random Graph Model-based approaches (ERGM). My contribution is related to privacy/ utility measures, and how such graph annonymization techniques could apply on evolving graphs.

    See project
  • Cloud based publish/subscribe model for Top-k matching over continuous data streams

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    Publish/subscribe systems are widely recognized in processing continuous queries over data
    streams and are augmented by algorithms coming from the field of data stream processing.
    Existing functions which are capable of matching publications & subscriptions in state-of-the-
    art publish/subscribe systems are depended on a stateless function which provides only a
    Boolean decision on whether a given publication is to be noti fied to relevant subscriber or not.
    But in such systems…

    Publish/subscribe systems are widely recognized in processing continuous queries over data
    streams and are augmented by algorithms coming from the field of data stream processing.
    Existing functions which are capable of matching publications & subscriptions in state-of-the-
    art publish/subscribe systems are depended on a stateless function which provides only a
    Boolean decision on whether a given publication is to be noti fied to relevant subscriber or not.
    But in such systems, the large quantity of received publications may be considered as a sort of
    spam, while a system that delivers too few publications might be recognized as non-working.
    In our study, we propose an advanced publish/subscribe matching model to control the
    unpredictable number of delivered publications over a continuous data-stream, where at a given
    time t our model limits the number of delivered publications by parameter k, while ranks them
    within a size w of sliding window. A general scoring mechanism is exploited where publications
    get scored against personalized user subscription spaces based on the relevancy. We adopt
    an inverted-list data structure to index the subscription space to enhance the efficiency of
    matching process. Also we focus on the problem of selecting the k-most diverse items from a
    relevant result set, in a dynamic setting where Top-k results change over time. We formalize
    the above problem of continuous k-diversity as MAXDIVREL which maps to the independent
    dominating set problem in graph theory, which is NP-hard. An incremental indexing mechanism
    is proposed for handling streaming publications that is based on Locality Sensitive Hashing
    (LSH) to diversify Top-k results continuously. Our prototype model is implemented in a cloud
    based message broker system and we have designed it to scale on top of Amazon Web Services
    (AWS): a scalable cloud-service provider.

    Other creators
    • Dr. D.N. Ranasinghe (Supervisor)
    See project

Honors & Awards

  • Winner, Grand Challenge, 3rd North American Social Networks Conference (NASN)

    International Network for Social Network Analysis

    The NASN 2021 Grand Challenge asks researchers to explore a Twitter dataset around COVID disinformation and share their insights.

  • Student Travel Grant for PODC '17

    ACM SIGACT

    Principles of Distributed Computing (PODC) conference held at Washington, DC July 25 - 28th 2017

  • ACM Travel Grant for Supercomputing '16

    Association of Computation and Machinery

    Acceptance Rate 12%

  • CINTEC Award for Best Computer Science Thesis 2015

    General Convocation - University of Colombo

  • Linnaeus Palme Scholarship

    International Exchange Programme administered by the International Programme Office for Education and Training and financed by Sida, Swedish International Development Co-operation Agency

    I was selected as one of two exchange students (out of 240) to continue education at Umea University, Sweden.

Languages

  • English

    Native or bilingual proficiency

Organizations

  • Association for Computing Machinery (ACM)

    SIGHPC Student Member and ACM Professional Member

    - Present

    ACM Membership ID 7974641 SIGHPC Student ID 5700546

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