Graph Ranking and the Cost of Sybil Defense

Gwendolyn Farach-Colton, Martin Farach-Colton, Leslie Ann Goldberg, Hanna Komlos, John Lapinskas, Reut Levi, Moti Medina, Miguel A. Mosteiro

    Research output: Chapter in Book/Report/Conference proceedingConference contribution


    Ranking functions such as PageRank assign numeric values (ranks) to nodes of graphs, most notably the web graph. Node rankings are an integral part of Internet search algorithms, since they can be used to order the results of queries. However, these ranking functions are famously subject to attacks by spammers, who modify the web graph in order to give their own pages more rank.We characterize the interplay between rankers and spammers as a game. We define the two critical features of this game, spam resistance and distortion, based on how spammers spam and how rankers protect against spam. We observe that all the ranking functions that are well-studied in the literature, including the original formulation of PageRank, have poor spam resistance, poor distortion, or both.Finally, we study Min-PPR, the form of PageRank used at Google itself, but which has received no (theoretical or empirical) treatment in the literature. We prove that Min-PPR has low distortion and high spam resistance. A secondary benefit is that Min-PPR comes with an explicit cost function on nodes that shows how important they are to the spammer; thus a ranker can focus their spam-detection capacity on these vulnerable nodes. Both Min-PPR and its associated cost function are straightforward to compute.

    Original languageEnglish (US)
    Title of host publicationEC 2023 - Proceedings of the 24th ACM Conference on Economics and Computation
    PublisherAssociation for Computing Machinery, Inc
    Number of pages40
    ISBN (Electronic)9798400701047
    StatePublished - Jul 9 2023
    Event24th ACM Conference on Economics and Computation, EC 2023 - London, United Kingdom
    Duration: Jul 9 2023Jul 12 2023

    Publication series

    NameEC 2023 - Proceedings of the 24th ACM Conference on Economics and Computation


    Conference24th ACM Conference on Economics and Computation, EC 2023
    Country/TerritoryUnited Kingdom

    ASJC Scopus subject areas

    • Computer Science (miscellaneous)
    • Economics and Econometrics
    • Computational Mathematics
    • Statistics and Probability


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